You have a nice kit, my bodies are the R5, M6 MKII-seriously underrated little camera. thought about selling my 100-400mm MKII and getting the 100-500mm for the extra reach , lighter and fast autofocus. Then I realized I won't be able to adapt the 100-400 on my M6 ii (640mm @32MP comes in handy especially for small birds)
This is precisely why I wouldn't *trade* my 100-400 for the RF 100-500 (except that I could flip the 100-500, pocket the difference, and buy another 100-400. The 100-400 works on every Canon camera I own. And I have both of the teleconverters.