As far as IQ is concerned, my first-hand experience is that the 5DSR is better than the 7DII, and the 90D outresolves the 5DSR and has excellent image quality. The 90D is significantly better than the 7DII for cropping. I found the 7DII to be excellent at BIF, and my memory is not good enough to rate the 90D against it. You tend to post images perched or swimming birds so I think the 90D might be an upgrade for you if you want more cropping. Best to try it before getting rid of your trusty 7DII, or better still keep both for a while.
Thanks for the response, Alan, and thanks for your efforts in reviewing the 90D.