I don’t think these are great examples because Sony’s games tend to have pretty decent IQ even in performance mode. There have been a few games recently where the resolution difference between performance and quality modes is really jarring though. FFXVI is one - in performance mode, it’s really muddy and hard to make out what’s going on at times with all the particles and other stuff flying around. Looks great in quality mode, but then it feels like shit because combat is very fast paced. FFVII Rebirth is even worse in performance mode, it looks very low res.
If the Pro can fix cases like that it would be a genuinely noticeable improvement, not just visually but in how the game plays. Not saying there’s £700 worth of improvement to be had, mind you.