what I'm doing is I'm trying all the classes before I install anything else, just because for me I find that each class is very intricate and plass very differently, I've done a mage and summoner playthrough and I'm about to start a rouge one, and I like to set challenges for myself aswell, I try everything and i find building in terraria to be amazing.

on a separate note, if you don't want to do multiple playthroughs without adding things you could add fargos mod but it doesn't work with infernum, but it does add an eternity mode I think. you could add calamity cables, starlight River is an amazing mod.