The more the better. With good skills less matter

T1s are practically useless because they're slow and have no aaw immunity, which means you practically have to stay at default altitude and get eaten by AA or stay out of aa/aaw range and provide minimal vision.

In dogfights against T2+, you'll get eaten up and most likely won't get a single kill.

Most DB/TBs will outrun you and some will even kill your T1s.

T2s do a slightly better job at killing bombers but dogfights are still difficult, especially since there are so many high lvl cv players now a days (high lvl not high skill :P).

AAW immunity is still pretty weak so scouting is still difficult but more manageable.

T3s is when you start noticing improvements in the gameplay and from there on, it gets better. That is unless you go against a 120 overvetted crew, then you probably want to avoid those fighters.

Without leveling them on a BB it is nearly impossible to keep pilots ahead of the CVBO.

And, tbh. it is not that important... In a CV skill matters more than crew.

Once you reach T3 lvl you can always drag - regardless of nation and wallet.
You may not be able to shoot down the enemy all the time, but you will be able to keep him occupied. And if you keep him occupied over his own lines, you win.
Should he disengage, you are free to do some scouting or you can hunt for scouts/bombers yourself.

You do not need to win in a FP vs. FP engagement. You only need to survive it long enough.