> I have seen lots of near-fires/melted things from under-tightening, but I have never seen a single near-fire from overtightening.

That depends what you see as near-fire ;) I recently helped out a friend whose lights had issues after she installed a more powerful fixture, turns out that the person installing it overtorqued the wire in the switch so much it nearly sheared off probably already during installation, and came completely apart when I took the switch out of the wall.

Better be safe than sorry and use Wago clips.