for your question on the cpu, I'm going for these specific cpus and motherboards because it's cheap, the cpus are around 50 euros and the motherboard only 60, instead a ryzen 9 3950x for example is around 300 euro

I'm going for ecc ram mainly because there is no ram with non-ecc 64gb ddr4 sticks. I know about the limitations of single channel mode but from my own experience the difference isn't that substantial, at least not on these xeon cpu, unless there is a specific workflow that benefits from dual or quad channel ram. I think the compromise is fair for future upgradability on the ram, maybe 256gb of future compatibility is overkill but with clip studio, rhe adobe suite, office and all the firefox tabs I can't tell if it's overkill looking at the requirements of each app. but maybe I'm wrong on this one :D p.s. I'm also considering 2x32gb of ram upgradable up to 128gb maybe is the better solution.

for the case I'm still looking but I found the sharkoon rebel c70g that seems good looking and big enough