I have been shooting with the 7D MKII for quite a while now... I shoot mostly indoor judo and birds/wildlife (high fps)... I think it might be time to consider moving to an R body (yes I'd need an adapter for my current lenses)
My current lenses are the EF70-200 f/2.8 EF ;EF100-400MKI; EF24-105mm f/4L IS II USM and the EFSSigma 8-16mm
I would appreciate your opinions and insight.
I went 7DII to R7 also.
The R7 is the obvious choice, big improvement in AF, frame rate, ISO modest improvement, viewfinder histogram option etc.
The pre-buffer works but I have only used it a few times; only issue with this is keeping the shutter button depressed waiting for action is hard on the arthritic hands!
I am using the 100-500 for birds, often with the R1.4x. Backwards comparability with EF lenses is good to excellent.
I liked the R experience so much I also switched the D6 for the R6II.
The different way the AF works can take some mental adjustment but is 90% of the time faultless with subject and eye detect.
Down side is some rolling shutter on electronic shutter. I find the issue small enough to use ES rather than first curtain and keep the shutter life high.
I use the EF24-105mm f/4L IS II USM mostly on my R6II but tests showed it was fine on the R7 too.
I can't comment on the Sigma but I think issues are less likely with non-telephoto 3rd party lenses.
EF100-400MKI Probably ok, I know folks with the MkII were getting good results.
Only point is the R7 feels small light and less robust than the R7, but it does the job.