FWIW I've often nearly bottomed out one limit screw while the other was quite high. Everything worked fine.

There are manufacturing tolerances in the way the chainring and the derailleur are attached. There's a lot of parts in a derailleur so a lot of tolerances. Or, something could be a little bent.

The combinations that don't work well probably would if you got a longer cage derailleur and longer chain. Not that you want to use 42/34; it's better to have a shorter derailleur. I don't think limit screws are the issue.