Also, if it would be possible - and better - to replace the stock CPU heatsink+shroud with a 3rd party one. 

There are no good options of fan headers on OEM motherboard.  I suggest you use usb2.0 powered fan.

there is no suitable shroud for oem SFF case that I know but you can upgrade cpu cooler to a low profile third party one. Just beware you need to install adapters for Dell M3 studs that are used for the stock cooler.

@redxps630​ Thank you. I'm not familiar with usb powered case fans but I do see  that a recommended case fan, the Noctua NF-A8 5V PWM, comes with a USB adapter cable. Hopefully that will work?

Also I've just seen on reddit someone used a 5 way PWM hub which he connected to the CPU fan header. However I'm confused as to where that fan header actually is. I'm guessing it's where the shroud or heatsink is hooked up to. Gonna have to crack my case open again...

As well, another confusing thing is people referencing a SATA splitter (SATA power Y-splitter cable, SATA power to 4pin PWM adapter cable, or 4 pin molex to SATA... all way over my head), but from what I understand the fans don't have a sata port, nor does this computer have one either, so I don't know how either would work. Maybe I'm misunderstanding something?

For posterity I'll link a reddit thread where someone managed to revamp his 9020SFF, which from what I gather isn't so different from a 5060SFF, aside from the lack of an m.2 port, and some differences in the pcie slots. In it he has the full monty setup of 4 case fans.

https://www.reddit.com/r/sffpc/comments/higpi2/dell_optiplex_9020_sff_sleeper_edition/

And his update post: https://www.reddit.com/r/sffpc/comments/htp3jr/updated_9020_sff_sleeper_build/

imo it is risky to siphon fan power from cpu fan header. you may burn off the fan controller.  the sata to fan adapter may work but imo is messy.  if you could install psu outside case that would help create some front to back air flow in the cramped sff chassis.  no matter how many fans you add if you pack the case like a pigeon cage, gpu can hardly breathe 

@redxps630​ Dang. Thank you, I just happened to see on the Noctua fan amazon page that it warns not to hook it to the mobo on account of it being too much power as it is a 5V fan and that would be around a 12V connection.

From what I've seen people claim to have gotten a reduction of 10 degrees C with the fans, so while I still want to try and do this, how would I use a sata connector? I still don't understand how it would work. The ones I've seen use sata power to connect to something else, but where is that parent connection going to?

The only sata port I seem to have in my system goes to my HDD and from what I gather the fans themselves don't have a sata port on them, only 4 pin. I don't know where I'd even put it inside my case once I got it... unless the HDD itself will be used to feed power the fans via the HDD's connection to the mobo.

...

Okay, I got the fans installed. There's three of them, one NF-A8 FLX 80mm case fan in the front, one NF-A8 PWM 80mm CPU fan over the heatsink and replacing the stock fan/shroud, and one NF-A4x20 40mm fan in the back, which can only be installed with the stock shroud removed.

To use them I needed nothing more than a simple PWM Fan hub, a single 4 Pin female to 5 4 pin males, linked here PWM Fan Hub , PC CPU Cooling 4 PIN/3PIN Power Cable Hub Splitter Adapter. The CPU fan is hooked up to the pins labeled CPU, and the other fans are in Fan1 and Fan2.

The issue I currently have is twofold. Firstly, there's now a CPU 0 Fan failure message on boot - but the fan is spinning. I get no high temperature warnings either, so it's doing it's job to a certain degree.

I say 'certain degree' because on startup, and 10-15 minutes after startup, temperature readings with CoreTemp and NZXTcam show CPU temps above normal, in the 86-92 range (yellow to red grade). Only after shutting down some background programs (Discord, Everything, a download manager - standard usage programs for me) and a period of a couple minutes, did the temp grade drop to green, which is apparently  high 70s and lower (78 C to be specific).

There is also a slight discrepancy with my GPU temps, as before I was at 36-37 C at idle with the single case fan installed (the NF-A8 FLX), and now I'm at 38-40 C (38 being the stable temp 15 minutes after startup) with three fans working in tandem. I have read that high CPU temps at startup are normal and should drop, but I don't know about GPU.

Now, unfortunately I never knew enough to check the CPU temps with the stock fan on. I never experienced any problems however. I will eventually reinstall it for comparison's sake, and hopefully it won't be better than this Noctua fan. Otherwise, I have wasted my money.

@redxps630​ Oh and thank you. I unfortunately did not see anything like that on my mobo. 

Alright, quick update on this project of mine:

In lieu of extra case fans - in this case 3x40mm Noctua fans, I decided to undertake an alternative cooler option, the ID Cooling IS-55, not in the least because I am also attempting to get a CPU upgrade and want to make sure it stays as cool as possible.

This was very new to me and I had to fumble through it a bit, namely with how necessary it was to remove the mobo from the case to install the backplate. And that is very necessary. I'm going to attempt to attach some screenshots from CoreTemp of the stock, no backplate, and backplate properly installed performance for comparison's sake. After which I'll talk about the difficulties I had with getting the backplate installed, which were fairly substantial for someone new to this like myself.

As well, the cooler leaves ZERO room for a 3.5in drive caddy and optical drive. 

I had to remove both and put my HDD with an alternate WIN10 OS into an enclosure, and now have to rely on an external disc drive for this PC.

To start with, this is the stock shroud/cooler/heatsink/whathaveyou, directly after startup.

Next is the ID Cooling IS-55 without the backplate (and I'll explain why I didn't install it below). This example is the most egregious one, but during one of the lowest points of load during my benchmark of choice: 7 Days to Die. In another temp log, ten minutes later after having closed the game for five minutes, the idle CPU temps dropped down to 69C on Core #0, with a general range of 68-71C.

Here are the startup temps without the backplate. Within three minutes they dropped to an average of 66C and stayed there until multiple tabs and other programs opened. 

And here are the startup temps for the IS-55 with the backplate properly installed.

As you might see, the startup temps for the IS-55 are higher than that of the stock cooler. I honestly don't know why, but it's a worthwhile cost as the stable temperature during gaming remains lower. For instance, in 7 Days to Die with stock, I could expect 74-76C after an hour of playing. However with the IS-55 installed that temp is around 10C less (I'll have to log a concrete temp as I forgot to do it before, but I'll update the post when I do).

As well, the CPU startup temperatures do fall off, of course. That's no problem and having the backplate properly installed leaves no chance of the egregiously inappropriate temps that occur without the backplate. That said, the cooler is a bit noticeable sound wise - not loud, but its idle noise is more than stock. On the flipside though I haven't experienced any sudden surges of fanspeed that I would get with stock that made the PC sound like a jet engine's baby brother.

Now, onto why I didn't have the backplate installed before - the first reason being I had no idea how to remove the mobo from the case, and the thought scared me. That's no fault of the IS-55 and nothing here is to put blame on it - I am new at this, and it was inexperience.

Secondly, when I did remove the mobo and install the backplate, it put my IO shield out of alignment with the ports on my mobo. There are four metal, female threaded screwholes on the bottom of the case which the backplate sits on that forcibly raised  the mobo up with the backplate installed. This was a significant problem, as trying to resecure the mobo would cause it to bow due to the constant upward force from the metal points of the case. So not only did this cause disalignment, leaving me unable to plug my USBs and monitor and ethernet in, but it also woud bendthe motherboard like a CD if I went along like this. 

It took some time to figure out how to get past this problem. I almost sent the IS-55 back, however I saw that it should by all rights be compatible with my system. I tried pressing down on the mobo at the back to keep the ports aligned as I secured it - that didn't work, too much counter pressure from the opposite end. It was like a seesaw. I tried it vice versa, same result, and I wasn't going to force it like that.

What worked in the end was kitty cornering screws into the front of the mobo, to the case, and then in the back, then slowly working to make sure the IO shield was aligned properly. The lynchpin ended up being this big screw with a flathead that went into an area of the mobo labeled M2 (not the m.2 SSD slot, though its screw helped as well), that managed to help keep everything level.

After all that, I got the cooler installed. I had some troubles after, relating to RAM, thermal paste spill and clean up, and how annoying the IS-55 is to secure (better off unscrewing the fan, securing the heatsink, then putting the fan back on). 

With that said, the performance of the IS-55 provides a much more stable and effective performance than stock. It is certainly better, but I never experienced issues with stock before aside from the occasional jet engine tier surge. Ain't like that now, though!

Next I'm going to see if I can get the Noctua or thereabout 40mm fans installed into the back of my workhorse here, though for the time being, that's definitely not necessary. I hope this longwinded post isn't too rambly, and provides some amount of clarity or help to someone down the line.