I have R5 and R5 II, the autofocus of the R5 II is significantly faster with action (sports, animals) and keeps a specific object in focus better, then the faster continuous shooting also leads to more "good" photos (however, you have to sort out more photos overall). With more or less static subjects, there is hardly any difference to be noticed. Video quality was already excellent with the R5 (4K HQ in particular delivers outstanding quality at a relatively low data rate), but I have never recorded for so long at the highest quality levels that the camera overheats; the R5 II has additional reserves here.
As always "it depends" :-) Image quality is similar (there are some videos on Youtube on the topic), also comparison videos R5 vs R5mk2. In short: Landscape / static situations / studio = no upgrade. Sports/action/animals = definitely upgrade (precapture, autofocus, 30B/s etc)