It has space for a standard PSU inside, but I’m pretty happy with this one:
https://www.amazon.com/dp/B0785GRMPG
I’ve been running it for about 4 years now.
If you have a fat GPU, you might have trouble with additional PCIe cards. You’ll definitely need more cooling as it only comes with one tiny fan.
I like cryfs for this purpose:
True story: