Your two back button settings are exactly what I have been using since I finally got the R5 last November (ordered on 9 July 2020), AND I watched the August 2020 Whistling Wings Photography video recommended on this Forum. I ran into way too many instances where the only way to break out of a failed auto-focus was to switch to One-Shot and use the manual focus ring to bring the focus all the way back to the subject. When the R5 AF blows out to the background, or when it gets lost deep in the branches behind the bird, it is usually unrecoverable using an AF function. If you try to use AF, it might take a half-dozen stabs of the thumb or more to force single point focus to re-acquire the target (much less luck had with animal eye tracking). Usually that meant that the bird had flown long before I got it back in focus.
Based on another post to this forum, I added the AF Point Button, programmed to switch between Servo AF and One-Shot AF, and that plus a spin of the focus ring got me back in focus much faster. Now with 1.3.0 I can skip the switch to and from One-Shot and just spin the focus ring, unless I actually
want the One-shot-only MF tools from the AF 2 menu available . I tried it today with the 100-500 (with and without 1.4 TC) and it allows me to correct a blown AF very quickly.
I still find the AF on the R5 less reliable for small birds than my 7D Mk II with 100-400+1.4 TC, but when I get lucky, or force it to work, I get better images, especially in low light. IMHO, the R5 animal eye AF is a lot like a paraphrase from Longfellow's "Jemima" poem:
...when it is good, it is very, very good, and when it is bad it is horrid.