I was facing the same dilemma, and photo is a source of income to me. I made the jump, use Linux and Darktable every day, and experienced no frustration at all. I didn't try to run macOS in a vm though.

To answer your questions : it is quick, and I find it to be a very good replacement for lightroom. To me, it's actually easier to extend than adobe software, mostly because Lua is very simple and the documentation is crystal clear.

The best advice I could give here would be to give yourself a good dozen of hours of deliberate practice on Darktable, maybe more if you're into very advanced editing, but no more than a week.