direnv + Nix is a great combo, and once you've gotten going with it there are various options you can use to speed up caching or automatically rebuild in the background on changes.
For project environments, flakes don't bring much new functionality to the table. They are a nice new convention that is probably worth learning, and they do bring faster evaluation. But don't sweat it.
For project environments, flakes don't bring much new functionality to the table. They are a nice new convention that is probably worth learning, and they do bring faster evaluation. But don't sweat it.