At one work place I have the same Mac Mini as the OP - it generally handles plug ins and even tasks in video editors quite nicely, even without an external GPU. It is always Wavelab, which is sluggish with plug in graphics. On my Mac Pro in the studio with a fast GPU, WL Pro 10.0.20 has problems with several plug in GUIs again, e.g. from Plug In Alliance. It can slow down work considerably. I’m tired of reporting these things, because the same plug ins run absolutely elegant and fast in other hosts like Nuendo 10.2 on the same machine (as reported many times).