Both CPU and GPU loads seem to be quite high, it may be that this system is not as powerful for LFS which is quite unlikely, or that something else is using up its resources.
If not already, put a fps cap in LFS to 100fps. It's not good that CPU downclocks due to temperature, while 75C is relatively on the high side, unless we are talking about a laptop.
It's worth checking what WestlY suggested, if you also have a dedicated and integrated GPU, if it for some reason switches to the integrated one.