Greasy Fork

But there was one problem that has been bugging me for almost 2 months - every single page stops loading when I open YouTube in a new tab.
And also, Is there a way to reduce more CPU usage on YouTube since it causes problems on older machines since this week?

But there was one problem that has been bugging me for almost 2 months - every single page stops loading when I open YouTube in a new tab.

Should be caused by other extensions / settings.

You might try old version: https://greasyfork.org/en/scripts/431573?version=1132597

And also, Is there a way to reduce more CPU usage on YouTube since it causes problems on older machines since this week?

I don't know what caused the difference between new machines and old machines. Are you sure the higher CPU usage is due to this script not YouTube itself? This does not really reduce CPU usage. Just make it smoother.