Quick question, 'post game' implies that there isn't any new content in the main game, so I can just play that and buy the DLC later without missing out on quests, right?
Sorta. There are a few quests added into areas from the base game, but beating the base game first doesn’t preclude you from doing any of them. You can 100% the base game, get the DLC, then 100% that, you won’t be locked out of anything.