A:AnswerIt’s an all in one liquid cooler so you never have to mess with it besides maybe spray the radiator off and fans with some compressed air which you should do anyways.
A:AnswerMy guess is the pre built pc companies have existing contracts with the GPU manufacturers. They probably get their's first and the scalpers get the rest unfortunately. Once ethereum switches from proof of work to proof of stake the prices should drop drastically and GPU supply increases.
A:AnswerOk, one RTX 3090 is plenty man plus you can add a ram kit if you would like I recommend 3200 Mhz speed. With 64GB of ram, you can easily get high frames on ultra settings on any title.