I only ever played last epoch online once when my characters were playing up or something, and I didn't get very far before I figured out my problem - no idea what it was. As such I don't have much experience with any shops trying to sell me anything.
I think version I bought had some cosmetics but they don't show offline so I may never have seen them.
Steam shows they are mostly pets that didn't show offline when I played. One was a different portal graphic
Not sure about seasons, its been a while since I last played - April last year was my last time in game.
Grim Dawn - I wish I could play this without deleting characters... but I hit the Steam save file maximum. I didn't even know they saved online. Maybe I wait a year and then just delete a few randomly.
Grim Dawn is what Titan Quest 2 might be in a few years after expansions add new characters to combine. I fear only 4 characters will get stale fast. Not that many combos to be made.
Hopefully TQ2 won't have gaps in gear lvls like GD did at launch, they had to add an expansion into chapter 2 just to give players a chance of getting through the original route to next areas.