So I've tried a little bit of everything since I normally use 1D
cameras, use an EOS R at my day job, and have tried out the A9. Anytime the EOS R freezes the frame between shots, it just feels really unnatural to me and it honestly throws me off. It makes everything into a bit of a slideshow effect where I find my muscle memory is slightly overreacting because the image view is still showing where things were after I've already moved, versus not showing anything and letting me assume motion. It's been a big annoyance to me on the EOS R. I know this is a hugely personal preference and some may not feel the same, so this is an area where I'd appreciate a user setting to decide.
In regards to the 20 FPS electronic, I'd prefer it to work like the A9's 20 FPS. Nothing changes or slows in the viewfinder when you take a photo except for a white box around the frame. As much I did not like the A9 for other reasons, I'd say this is the best-case scenario, since having a nonstop live feed of your subject is the absolute easiest way to track your subject.
You are right though, the EOS R has a lot of warping in electronic shutter, but I hope the 20 FPS of the EOS R means they have a much faster sensor readout with less warping. Most of the assignments I do at my day job are slow-paced and I've been able to use the EOS R's silent shutter when I really need to, but most of the time I use the mechanical shutter anyway to save me from losing any images to bad warping with sudden movements.