MD770 Classic White/BKF

Have you considered Mistel Barocco MD770? Has everything you've asked for: fully split; either half can be plugged in on its own; slight tenting with rubber feet; palm rests available as an optional extra. For increased thumb usage, look into Arsenik or Kenkyo (as a software solution on any keyboard

This really depends on your budget and keyboard size preference. I’d recommend looking at the FAQ guide on the mechanical keyboard subreddit. Personally I like small (60-80% TKL) keyboards. I used a Royal Kludge RK71 for something like 5 years. I currently use a Mistel MD770 spoke keyboard for work,