I'm in the same boat here. The only two things I don't love about my R5 are the buffer and the (slight) electronic shutter warping. The 1dx2 and 1dx3 buffer is actually unlimited, you can fill any card before it hits the buffer. I would bet the R3 can match that, easily. Whereas the R5(and even the A1) both have a buffer of maybe 50-80 raw images. That sounds like a lot until you're holding down the shutter and hitting the buffer in 2 or 3 seconds of action. Whereas on the 1dx mark II, if something incredible is happening, I can just hold down the shutter for the next 30 seconds and have every single frame in perfect detail.
I am more than happy with my 1dx2 as a secondary camera to the R5, but like you said, it's annoying having duplicate lenses to worry about.
In all reality I'm actually very excited by the idea of a usable 30 fps. On the R5 I tend to avoid 20 fps due to buffer/file size, but at 24 mp I'll be less worried about file size.
If Canon implemented a way to control the FPS of electronic shutter, I would use the crap out of 20 fps at 24 mp.
In rough nonscientific math, 45 mp at 20 fps is ~900 MB/s, 24mp at 30 fps is ~720 MB/s, and 24mp at 20 fps is ~480MB/s.
