I kind of echo your Psychonauts 2 thoughts. I did play it/finish it and while I reasonably enjoyed it, it felt very lacking compared to the first game. I'd say only the PSI-King level is really unique...
Alchemic Bounty breaks the game entirely (especially version 1.00 with an item dupe glitch). Even on the newer patch, you'll still get a ton of materials to sell/use.