I’m currently able to set my 40 man postseason roster. Do I just promote them all to the majors? If so do they get a salary increase? Because I’m pretty much capped in salary. Also do I promote them right away even though they’re in the thick of the AAA playoff race?

Yes, they do get a salary increase. Generally, I would leave them in AAA if you are still in a playoff race there...unless getting them to your ML roster will help that team make the playoffs. Also remember, though, if your ML team already has a playoff spot locked up and you want 1 or 2 or your current AAA players on your ML, playoff roster, they will not qualify for the first round of the playoffs unless they are on your ML roster by the last day of the regular season....I think. I could be wrong on that.

As long as they are on your 40 man by roster expansion , they are playoff eligible.