I've built a few small form factor gaming PCs over the last 5 or so years. The heat produced is directly proportional to the power consumed. If you're worried

I've built a few small form factor gaming PCs over the last 5 or so years. The heat produced is directly proportional to the power consumed. If you're worried about your components overheating in a small case, there are absolutely ways to cram a ton of performance into a small package. You can fit top of the line gaming hardware in as little as 10-15 liters of case volume. If you're worried about your PC becoming a space heater, you'll need to go with less power-hungry components, but you can still absolutely build a tiny and capable gaming PC.