No umatrix provides finer control and is definitely useful along with your adblocker.
umatrix is available as part of uBO by clicking I'm an advanced user.
Why is this?
Presumably because an adblocker, like virus detection, consumes potentially non-trivial CPU, and may introduce race conditions of extensions applying deltas to a DOM which results in rendering and behavior bugs.
adblockers are just filters and aren't scanning your files like an antivirus, little cpu used I imagine.
uBlock origin's lede is "Finally, an efficient blocker. Easy on CPU and memory." Ad blocking, pre-ublock, could take noticeable resources.
The different apps do the same thing and end up competing for resources.