I think having post-Namek Chaozu above Gurd like his filler self is fair, given the gains Piccolo made from far less of the same training. After that, he has nothing going for him in the series and you could assume he hit a wall after trying to adjust to Earth training and didn't get much stronger. Peak Chaozu would probably get no further than Reacoom/Butta/Jheese imo, psychic powers or not.
If we use his Super filler self who paralyzed post-God Base Galu though, he could solo Z for all :toei care.