coyote6
Adventurer
Unlike fantasy genres, where the violent & often lawless nature of the world support the adventuring party, science fiction typically brings constraints (as well as opportunities!) that are unavailable in the fantasy genre.
Fantasy genres generally only have violence & lawlessness because they're set on frontiers, or in times of strife and war. Think of Westerns -- Deadwood & Tombstone in the 1870s might've been lawless regions, but New York, London, Paris, etc. all had plenty of law. So set your SF games in those lawless areas -- rim worlds (like Tatooine in Star Wars), borderlands between multiple interstellar powers (such that no one of them dominates, and no one local is much interested in law or order), and just plain old corrupt worlds -- or during wartime (e.g., Casablanca). Then there's Firefly -- the Serenity's crew are pretty much the definitive PC party, and they got up to no good all the time. Meanwhile, there was plenty of law and order -- elsewhere.
Chris Bunch's Last Legion books and Walter Jon Williams' Praxis novels are all set in the immediate aftermath of the collapse of the gigantic interstellar government, and all the various greedy & power-mad types are scrambling to set up their own fiefdoms. That leaves plenty of room for PCs to adventure.
2. Troubleshooters.
PCs work for corporation or are freelancers for hire.
Pros: Supports “Adventuring Party” style play.
Cons: Characters are criminals/must work outside the law. Genre setting “conceits”, i.e. cyberpunk.
Nah, it doesn't have to be cyberpunk -- you don't need dystopia, a computer matrix, cybernetics, or most of the cyberpunk trappings to have corporate troubleshooters. Plenty of non-cyberpunk SF have powerful corporations, in settings that are transhuman or space operatic or otherwise not very c-punk.
The PCs don't have to be criminals, either -- posit a world where interstellar corps have vast legal rights (a la cyberpunk games), and let the PCs work for such a corporation. Or take Stross's Iron Sunrise -- the PCs can be troubleshooters for an extra-governmental organization, a la the Eschaton or the like.
Heck, see also modern day PMCs -- they operate a lot of places, with lots of military weapons, and aren't generally considered criminals (though some of 'em seem to get up to no good). So let the PCs be members (perhaps the whole outfit) of a licensed security/military/troubleshooting corporation, and they can get hired by whomever to do whatever. Legally.