I would like to add that the reason I went with these cpus is because they have the highest base clocks which is their speeds out of the box without any overclocking. Now you can opt for the other cpu options you gave but they are a tiny bit slower at base but if your friend overclocks he can easily close the gap. So it really boils down to the pricing and as I can see from this moment the cpus are around the sme price all around so might as well get the best ones if you gonna pay around the same price anyway. But by all means replace the cpus if you find a deal or something. For the intel build if you do decide to get the i9 9900k you will need to chsnge the motherboard to one that supports its socket and you will need to check what ram speeds that motherboard supports. If you don't you can just buy everything on the list I made. For the amd list you can just switch the cpu to the 3700x and you don't have to chsnge anything else.