This is an orange pi 5 without cooling. Perhaps it can’t reach the maximum because it has a thermal throttle? The CPU temperature is 42 ºC.
I’m using the same program in another computer and it uses more CPU and in a more consistent way. Without the lines being all over the place.
Yup, I agree.
It looks like ffmpeg is using about 1/3 of the processing power, but this is likely intentional, because if it froze your computer you’d be pissed.