For the US tree, the furthest I got was the T29. For the Soviets, I unlocked the T-43. Definitely prefer medium tanks. From what I remember, I liked all of the medium Soviet tanks that I unlocked. I have enough silver to unlock the T-44 but am kind of interested in trying some other nations. But am happy to keep grinding the Soviet mediums if they’re worth it.
I generally like to be somewhat active, not passive. I always have a great time flanking.