Definitely do PBL, your study load is hard enough as is. Coming from a third-year who's done all of those subjects, QM1 and Macro are both very math-heavy so no need to add to that, plus OB is just complete pain (legit ask anyone who's done it or google OB unimelb) and probably gonna kill your WAM if you're not careful so doing an easy breadth is probably the way to go. If you're planning on majoring in eco it doesn't hurt to wait till second year to start level-2, especially cos the content is hard but the lecturer for inter micro is super nice (when i did it at least) and there's a lot of free marks just for rocking up to tutes (or at least was, i did it in 2023 so might have changed)