is the delay or image quality to low on the EVF vs optical? too much battery? interaction between the live view and EVF? I'm really curious (in an I want to learn more way) why after buying it you think this.
The two types of photography that I engage in most often are birding and product photography. If I frame the question of what camera to pick up as "What does an EVF do for me that's advantageous?", the answer is, for the two types of photography I like, not very much.
In product photography, whether ins studio or at location, almost everything is lit with strobes anyways, so you don't really get a preview. Although the EOS R isn't a disadvantage, there is also nothing extra that it offers. And anyways the camera is on a tripod and I'm using live view + tether to a PC, so the VF isn't much of an issue.
I haven't really done much birding, because I've been busy with other stuff, but some minor stuff aside (like preview on the LCD and some ergonomics changes to get used to), It just doesn't really give me anything over OVF, which I still find more enjoyable to use. I do really like focus magnification, though, particularly for bird portraits.
To me, mirrorless is a cool novelty, and I'm happy I own one, but it just doesn't really give me practical advantages in what matters most -- increasing the keeper rate. In the winter, I'll try to catch some owl photos, and in the spring, when I typically do more birding I'll see if that holds true. I do like the new RF lenses, but I haven't bought one, because 24--105/4 is just not something I want to invest more money in (too much overlap with lenses I already own, that are great), and the 50 is just more than I want to spend for a FL I don't use enough of.
I will say that I'm really impressed with EOS R's AF in a variety of imperfect lighting situations, much more so than A7R3, which gives me some hope for birding, but I really don't know. If those birding adventures go really great, it will vastly improve my chances in investing in future RF bodies. A lot of times, I think something might work out one way or another, but it's impossible to tell until I actually get out there and do it.