Newbie question about hitting limit, but not with auto mode

Hello, I am on a pro subscription, I have a hard time understanding this limit thing. Auto mode is working fine, but as soon as as I choose a specific model, it tells me that I hit my limit.

Should I switch to pro+ ? if auto mode is working fine currently what does that mean ?

do we have better performance in auto mode when using Pro+ ? or as long as we are in auto mode, Pro is equivalent to Pro+ ?