[Dream™]

Most miners actually use a a certain '%' of the GPU / CPU too make sure the victim does not notice or their computer is dog slow.

[Adventure T1me]

It depends on the amount of threads
I personally use 4
4 threads usally result in 100 % CPU

if you want to use less then go 2 threads which can usally result in 50 % CPU
(depends on the computer)