This is pricey for a fan, but you'll never have that problems with noctua
This one is what I use in my 'desktop' [Fractal case] Plex server since 2020:
amazon.com/gp/product/B0085FT2JC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
You'll use these cables:
https://www.amazon.com/gp/product/B012BPLYJC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Look up fan mod for the card, I used this little boi:
https://www.amazon.com/gp/product/B009NQLT0M/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
It's basically plug and play. The fan "modification" isn't too hard. The card is considerably cheaper now than it was in 2020. My server is completely stuffed with something like 9 drives and 3 SSDs plus a GPU so the fan mod was to keep the temps 'reasonable' in my stuffed case.
I run this fan and DC-DC. Works great and practically silent.
Noctua NF-A4x10 FLX, Premium Quiet Fan, 3-Pin (40x10mm, Brown) https://www.amazon.com/dp/B009NQLT0M/
eBoot Mini MP1584EN DC-DC Buck Converter Adjustable Power Supply Module 24V to 12V 9V 5V 3V (6 Pack) https://www.amazon.com/dp/B01MQGMOKI/
Parts List
PSU to Board:
Wire: https://www.amazon.com/dp/B08HSC5NW5
Connectors: https://www.amazon.com/dp/B08HK1Q4F6
Crimp tool: https://www.amazon.com/dp/B00079LN1Y
You can get away with 14 gauge steel wire I believe but going thicker just makes things a bit safer with this kind of amperage. The connector kit is overkill too but I can't remeber which size I needed. I do remember having to trim the sides of the connector rings to fit inside the terminal space. You don't have to use connectors at all but it gives a more secure connection. You can get away with directly clamping the wire under the terminal screws if you prefer though.
3 pin to 2 pin adaptors
3 pin: https://www.amazon.com/dp/B01DUC1PGC
2 pin: https://www.amazon.com/dp/B09KH68WVL
I just solder the wires and put some heat shrink on them so I didn't have to change any of the factory wires.
Dual z wire for second stepper
https://www.amazon.com/dp/B0823QJJ8C
Optional fan upgrades
Board fan: https://www.amazon.com/dp/B07CG2PGY6
Heat block fan: https://www.amazon.com/dp/B009NQLT0M
The octopus can run fans at multiple voltages so you can swap the factory fans for quieter more efficient nauctua fans. The heat block fan came with an adaptor but I had to rig one for the board. I just can't remember how I did it. That said, you may end up needing a different board fan depending on the enclosure you print.
You need to print a board enclosure and PSU enclosure since the wires don't fit through the factory enclosures properly. I can point you to the stl files I used if you want.
Sure! I'm assuming you're running a fully stock hotend. If that is the case, then the only fan that will fit, without modification, in place of the existing hotend fan is the NF-A4x10, 12v. That fan is OK especially if you do not plan to change to an all-metal hotend, but some people have reported that the cooling capacity is sub-par compared to the stock fan.
The better option would be to run a NF-A4x20, 12v fan. That fan will not fit in the existing hotend shroud, but I thought about mounting it on the outside of the shroud, which MIGHT be possible, or you can look into completely replacing the existing shroud with one that would fit the bigger fan (print in PETG if you do!) This fan should be more than sufficient if you only ever plan to run the stock hotend, but when I upgraded to an all-metal hotend, using only this fan I lost the ability to print PLA and PETG due to excess heat-creep resultant from insufficient cooling.
TLDR:
For the stock hotend this will fit in the existing fan slot and provide decent cooling
For a non-stock/all-metal hotend run a better fan or (like me) a couple noctuas since the one 40mm noctua of any size doesn't seem to be enough
EDIT: if you go with the noctua, red and black go to the red and black wires (obviously), and you can just clip the yellow one it doesn't serve any purpose in this setup.