If you're specifically looking for M+, one way to get more info is to look at what the top players are using in M+. Check for example on
Subcreation and you'll see it's mostly between Tempest (47%), Magistrate (31%), and Paragon (21%). The differences probably arise from people swapping between things on Tyrannical vs. Fortified weeks.
Other than that, the usual suspects are probably your best bet, i.e. written guides and the class discords. There's usually a lot of people putting together information there (especially on the discords) so you can benefit from their collective wisdom.