Hi there,
I'm no pro but I can give you some tips (are you playing 1v1 or any other mode?)
First of all, t70 got nerfed couple of patches ago so it is not so strong as it used to be.
Second of all, if you can field it until 8-9 minutes, go for it...but don't use it alone, support it with your infantry. Because if you get fausted and enemy has pak nearby, it's bye-bye t70. One teller? Also dead t70.
If enemy gets p4 before your t34 (and you didnt go for t70) then he had better fuel control.
Penals? These days almost no one (again, speaking for 1v1) goes for penals, usually it's cons...
t34/85 is probably still the best medium in the game.
Hope it helped at least a bit
