Glad it has worked well for you, it has been a mixed bag for me. Focus acquisition and accuracy was abysmal on my EF 70-300 f/4L + R6 + genuine Canon adapter
That's pretty strange! I have the R6, and I have the 70-200 f2.8 L (the original one, released in 1995, so realy old tech and electonics); focus acquisition and accuracy are top notch, both in the studio (which is kept pretty dark, so I don't give AF much help) and in location.
And its speed and precision are top notch even with two 2x EF Canon Extenders stuck in a row (so having a practical 800mm f11 at the long end).
I admit that if I throw in the third extender (an old Kenko MC7) then the AF surrenders 95% ot times (but I got a couple of lucky focus locks, so it can be done; one extender + kenko focus without problems), but I'm pretty sure it's Kenko's electronics guilt, I feel a third original extender would still retain AF even at 1600mm f22. Never tried on R10 but I expect the same results.
For my experience (more then half of my lenses are EF, and will probably forever be) the EF lenses on R systems works better then what they were doing on DSLR's.
Especially I can vouch for the Sigma 50 f1.4 which I always had problems with consistence and accuracy at f1.4 especially for portraits at close distances (with so little DoF, me and/or the subject slightly moving between focus lock and actual shutter actuation, makes all shots critical) with my previous camera, the 6D; the hit rate for tack sharp was under 50%, I thought so many times to sell it due to frustration, it was a nightmare lens.
Well, with the R6 (in single shot, not in Servo) the hit rate is 99% tack sharp, I don't miss a picture anymore; the 50 f1.4 literally has reborn again, and now is my favourite lens for available light outside the studio. And all the other lenses are as fast, or faster, and super accurate; so I really can't see the R system as anything less then a gift for my EF lenses, which gained a second, and better, life.