I have a fixed group of players that isn't going to change. Better to say, several "groups" of 1 to 3 mostly socially awkward friends who don't want to have people they don't know behind the table, which means that I will not be able to recruit more.
Most of them, except 1 or 2 players are new to RPGs, so I don't even know their playstyles, and I am considering an option to run a premade adventure, but as I have read on the internet, they typically require a given amount of players, and changing it causes balance problems.
What options to adjust the party do I have as a GM, what are their drawbacks and advantages?
Right now I am just learning the system (Pathfinder), and the reason of asking this question is that I want to know if I actually have viable options and can consider playing adventures designed for bigger parties, if I should better avoid them, or if I should avoid them at all cost, huh.
A good answer would contain a list of both good and bad options, with either a detailed description of pros and cons or links to those across RPG.SE.