Thank you a lot, I’m all in for having a rolling nvidia driver again 
as for the reasons one can read my thread here:
Since driver versions 418 - 455 all support the same gpus (455 supports new ones ofc but didn’t drop support for older ones) it is safe to remove all from 418 - 450.
But I would advice keeping at least the 390 legacy driver if possible since this is the last series supporting older gpus which are dropped from 418 on.
If this is too much effort it may be enough to have the 390 series only for LTS kernels.