It would be beneficial to qualify and clairify this a bit. Those that talk of finding f/11 the right aperture are mostly 1) using a FF (not APS-C) body and 2) referring to extreme corner edge sharpness, not general overall sharpness. The center of the frame will be very sharp at f/8 or more open, even on a FF high MP camera. If you are photoing an animal in blue water you can open the aperture wider. If you are photoing a very detailed reefscape and sharp extreme edge corners are critical, then f/8-11 would be best. Keep in mind APS-C sensors, like your R7, are generally much more forgiving than high MP FF systems. There is no hard rule as it all depends on different subjects, objectives, and the conditions you are in.
Yes, the Canon EF-S 60 works very well with the RF-EF adapter. That will give you a 96mm FF equivalent, similar to Canon 100 on a FF, which is a great macro choice.
Perhaps I missed something, but in the opening you mentioned you mostly like wide angle. Specifically that the Tokina 10-17 is the perfect uw lens. Keep in mind the Canon 60 will be a narrow solution, not wide.
The important thing is that you settle on a solution that you feel best fits your needs. Congrats and enjoy!
(....as background, I have used the WWL as my primary solution for over 5 years and logged 800+ dives with it. I also use the Canon 8-15 w/ a 140 dome. Prior to that, I used the Tokina 10-17 w/ Zen mini dome and Canon EF-S 60 on Canon APS-Cs for 11 years.)