Similar boat to you, I sold my 5D MKIII and went for the EOS R with a bit of a leap of faith but the new mount and future possibilities pushed me (even if I find myself quickly upgrading to the next release... I mean I pretty much did that with the 5 series). I sort almost relished a fresh new start. I am a casual shooter and sort of just walk around with my camera so I have been tempted by size (ideally weight too, but this EOS R still has a heft) advantage of mirrorless for a long time now but didnt want to sacrifice too much on SLR handling and performance, so was waiting for an excuse to go for it.
I've taken it out on a few outings with the light weight 35mm RF and the budget 50mm 1.4 EF (the 35mm RF hadnt been realsed when I bought the body). My theory was that a budget RF lens would be inherently better quality than a budget EF lens.
I think the biggest blocker to perfection is battery tech, battery tech hasn't caught up and is struggling. I ended up buying a 2nd official battery after the first outing! So to get enough juice for a days shoot you need to have the power saving profile enabled all the time which means there is a lag from when you press the button and the EVF comes alive once the camera has gone into a power-saving sleep mode. I am not sure how much the EVF performance can be tweaked but when I turned off auto-power down on everything, the sensor turned the camera into a pocket oven lol. Now I am back home I will have more scope to play around.
The EVF power-up lag and to a lesser extent battery time is what I am really stuggling with compared to the instant viewing and response of the SLR. I find myself having to half press the shutter button now and then in anticipation of a shot. I also noticed the EVF does not always pick out small moving details like distant birds flying around in the sky, I am not sure if this is another power saving thing (I know you can increase the performance of the EVF) or a technical limitation of the screen resolution and DR.
Settings wise, I was a bit frustrated at first. I certainly turned off auto-preview, and reverted to just viewing images using play button as and when I wanted to, I found having the image appear in the EVF just after taking a photo very disorientating almost nauseous! Others may differ. It may also save precious battery time. I love seeing the horizontal rule and other info in the EVF, that has been really useful for me. I havent yet got into a habit of changing options while viewing the EVF preferring to revert to the rear screen for that. Maybe an old habit not sure.
Ultimately I would prefer to have the option to turn the rear screen off completey and parked to save on battery and for protection when day-trekking but without any other viable option the rear touch panel is vital for AF point selection. I have mine set to top right corner, absolute for AF point selection, as I tend to jump around the extremes of the rule of thirds. Would be nice to have an option to just set the rear screen for AF point selection to save on battery juice. I quite like the touch panel for AF point selection but its not perfect, I find the reach to the left-side AF points awkward and the lack of alternative options for the reset-to-centre button bizarre. I struggle to reach the "Delete" button intuitively. There is a known bug where the AF selection suddenly moves to the far bottom corner which is frustrating.
The touch bar thing I havent used yet, I would have liked it as Exposure compensation bar but no option to do that (seemed to be an obvious use for it). I might set one end to activate face/eye focus as Ive found that surprisingly useful for doing al-servo portrait shots while on the move.
I keep forgetting that there is a dial on the 35mm RF, Ive set it to exposure compensation but it feels a bit awkward compared to the old wheel. I mostly put up with the slightly inconvenient default rear dial.
Ive started to notice the quality difference between my current low end lenses and my old L lens range but was shocked by the weight of the new RF L lenses, although the 24-70 looks like it might be a good compromise option. I can't afford any lenses at the moment so happy to wait and really enjoying the combined weight and size of my current kit.
Oh and I bought a new strap as the Canon one is awful!