I have the most fun at the endgame, at the level 45+ range, smashing big fleets with a varied combination of overpowered ships. I just wish there were more big fleets aside from Hegemony System Defense Fleets (Tri-Tachyon Security Detachments are not big enough).
I dislike early game because you start with junk equipment, limited hullmods, and too few OP to get everything you need. Simulator (and some missions) can replicate early game conditions very well, but cannot replicate big fleet battles beyond that part of the game. I can see early game being a bit fun, where you need to think a little to survive. It is just too low powered for my tastes.
I hope the finished game will not punish you for excessive fighting, aside from making new enemies I wanted to fight anyway. Non-combat stuff are the grinding, um... means to the fun stuff - fighting. My plan for the game is to build up everything I need, declare war on the ENTIRE sector, fight everything, and win. Why fight everything? I get the most variety of opponents when all are the enemy.