PokerTracker

When I'm playing a tournament, I only want to see other players' stats for certain number of players (ie, I expect most players to play differently when it's three-handed compared to nine-handed). I edited my HUD options to try to make this happen, and expect to see stats for each player for 7-10, 3-6 and heads-up but I'm not getting expected behaviour: I still see the player's entire hand history for the tournament. Why isn't this doing what I expect, and what is this doing?

The settings under 'Profile Select' in your screenshot are for what HUD Profile is selected to be used on the table. If you want to filter the data in the HUD based on the number of players then you will need to instead set that up using the 'Number of Players Filtered' section which is under the 'General Settings' tab:

Guide: HUD Options & Profiles (Filters)

Video: HUD Options