Thanks for your answer!
My issue with the motherboard is that the ram is stuck at 1600 MHz and XMP isn't working ?
It's most probably me which sk somewhere but then it's not an upgrade topic anymore.
but for the CPU, I oftenly find myself stuck quickly at 100% usage in games where the GPU tend to stay much lower (and I thought it should be at a 100% for the GPU most of the time).
Could this come from the fact that when I open the taskmanager, the GPU use isn't "properly updating because of "tab changes" or something?
In anycase, if there isn't a problem on the spec but on my param somwhere, you helped me not wasting my money on something useless so thanks !!
though it means i'll have to bother understanding wtf is happening then ?