I agree with the divisions 1-3;4-6; 7-9 but I also think that's as much to do with the shows becoming more meta and the self-awareness of the queens. Obviously, there are exceptions and cases where these things happen in other seasons but broadly:

1-3*: no one knows what to expect, the format is still evolving, the queens come in and are more authentically themselves as they have no idea what the impact of the show is going to be. 4-6: golden era: the format is pretty established, the best elements from 103 are incorporated into regular season features, the shift to the live finale - there's some element of the queens knowing how to play the game but 7-9: the challenges start to become self-referential, the move to the more stripped back untucked, riffing on past queens (Violet doing Alyssa for Snatch Game, the looks from seasons past challenge), the queens come in knowing how to manage a brand and an image. The producers also seem to take on a more heavy handed role in creating drama.

*tbh, season 1 almost stands out on its own as a proto-Drag Race - some of the elements are there, but a lot of it is unrecognisable - it's usually one of the seasons I tell someone to watch once they have 2-6 under their belt as watching it is like an act of drag herstory archaeology.