I was worried about EVF lag, and that is why I was hoping for one more successor to the 7D2 (a more "professional" 90D), but lag has not been much of an issue at all. I bought an R5 and was very happy with the EVF. I really like the way that the R5 and now the R7 can identify faces and eyes and lock onto them, and AF with almost any open f-number, but there is one aspect of AF that is much weaker with these mirror-less cameras than with DSLRs; the depth in the field at which the AF can "see" is much shallower with image-sensor AF, which causes the AF system to get stuck, often losing what would otherwise be ideal photo-ops. For example, if I focus on a bird on the front of a bush 25 feet away, and it flies towards me and poses like a model on a fence 8 feet from me, a bird photographer's dream, both cameras will stay focused on the background, and act as if they have already achieved focus. Neither camera offers any kind of button assignment to nudge the AF, and many lenses have no manual focus override, or the ones that do have too slow of a focus ring speed to get close to focus in one twist of the wrist. With my 400/4DO II, it can take 4 or more turns of the focus ring!
So, even though when focus is already close, these cameras can be miraculous compared to DSLRs, they are completely unreliable for focusing on anything that is suddenly much closer. The ironic thing is, with DSLRs, the faster your lens, the better the AF speed and accuracy, but with the R5 and R7, the faster the lens, the more likely the AF will stall when a subject is suddenly very close, because the fastest lenses have the least DOF wide open!
