cooling matters yes, that doesn't necessary means water cooling,
My machine is fully air cooled, but I did think it through and used selected parts for cooling.
GPU is an ASUS STRIX with a big cooler, and i have a Noctua NH-D15 on the CPU which is in itself a beast. the case is a basic silent one (corsair) but with 4 14cm intake fans, to keep a positive pressure inside the case.
The biggest heat producing element is the GPU peaking 74 to 80°C . And since I built this machine, I have completely shutdown the heating in the room, if i'm cold, i just have to do a few hours of flying.
I think a lot of planes are scripted, Ixeg use Lua scripts with GIZMO, FF use also lua scripts ut with SASL, I guess it's the only way to build planes for xplane without being limited by the standard features and be able to program realistic behaviours.