I checked one my recent "heavy" projects and it's only using 9gb out of 16. I'm also on OS X 10.10, though, not Catalina, and don't know how RAM requirements differ.EDIT : Sorry, I just realised you asked me about ram and VST plugins.. I can barely make do with 32 because I do orchestral mockups with tons of sampled instruments.. But disk streaming gets me the rest of the way.. If you are only using algorithmic rather than sampled based stuff, you can get away with 16GB.. but really, this is 2019.. Mojave is ram hungry, I am not sure about Catalina.. I think 16GB is the bare minimum to *scrape* by.. I would NOT like to be on 16Gb, honestly. Even when I am using a few safari tabs I have 17Gb available out of 32.. This means I'd be maxed out on the 16Gb model (as I was on my 2014 MacBook Pro).. I have to shut everything off when I load logic or Cubase to make or mix music.. I like having headroom. My iMac pro has 64Gb ram, and I have managed to max it out on a huge project.. so.. yeah.. it really depends on what sort of music you make. When I am making EDM for my own pleasure, I don't use much ram at all. When it's serious work, I do.
32gb would be nice to future-proof, but $400 seems like a lot for something that's never been an issue for me. Going to have to think about this.