The fastest supported hardware on windows XP is a 780ti on a socket 1155 or 1366 platform. I good setup for XP IMO is an i3 sandy or ivy bridge with a good clock speed and a gtx 960 or equivalent.
With a simple inf mod you can get a 980ti working, and it is possible to slipstream SATA drivers for socket 1150 with Z170 and Z270 chipsets if you want. So theoretically at least you could get an 8600k or 9900k with sli 980ti's running in XP if you wanted. Theoretically.
If you are playing games from 1999-2002ish you can run into compatibility issues here and there. A lot of that has to do with later drivers on later era XP graphics cards. I have had a lot of success fixing these issues by using GoG releases of games on windows XP.
I have tried to run my XP gaming collection on my modern windows 10 machine, with a haswell CPU and a GTX 1080. I had actually quite a bit of success, although most games required patching and tweaking to get working properly, or to take full advantage of modern displays.
https://docs.google.com/spreadsheets/d/1oSWRc … dit?usp=sharing
Basically pcgaming wiki is your friend.
I would say the biggest hurdles for running XP games on windows 10 are:
-Compatibility with windows directx 7 or earlier is pretty bad
-Getting EAX working can be pretty difficult. Not all games will run through alchemy.
-If you are using original media, you will need a CD crack, and some of those cracks do funny things according to arbitrary appeals to honor by software pirates of the time. For example, the no cd patch for warcraft 3 breaks the final mission in the campaign.
-Gamepad and peripheral support was mostly a miss for me, especially with Xinput devices.
I have at one point used a gtx 960 and 2500k with XP and it worked just fine.