I don't have a hard system and don't plan on having one, but broadly you'll have the pros and cons of the legions. Specifically...
[] Ultramarines
You're codex compliant, more or less. That means your generic but have no particular holes
[] Space Wolves
You're a bunch of crazy wolf guys. Canonically they
have no successor chapters, so that'd make you a chaos warband per se by definition, I do believe.
[] Iron Hands
I don't actually know all that much about them, but I'd research for the specifics f it wins (that applies to all the legions I know too little on). In any event, they have a cybernetics focus
[] Dark Angels
I know they are sneaky and have a big fleet, and that the way they handle their fleet pisses off the Imperium. I'd have to research for further details.
[] Blood Angels
They have an obsession with art and (genetically rooted, super power) anger problems, a hilarious dichotomy given one's Slaanesh and the other Khorne from a Chaos perspective.
[] Imperial Fists
They were planet defense specialists, as I recall. One of the legions I know less on off the top of my head.
[] Salamanders
They are heavy weapons specialized, I think? Again, would need to research.
[] White Scars
SPEED BIKE GUYS THAT ARE MONGOLS OR HUNS OR SOMETHING. I'd, again, do research for details.
[] Raven Guard
SUPER SNEAKY, as I recall.
[] Alpha Legion
SUPER SNEAKY, convoluted plot guys. And them (and everyone below) is traitor legions so definitely warband and not renegade chapter. Technically chaos undivided but there's a bit of a popular fan theory that they are secretly loyalists. Oh, and apparently they use cultists. A lot.
[] Black Legion
Essentially, they are 'generic' chaos. Chaos undivided, accept chaos marines from all backgrounds.
[] World Eaters
Khornate by default, mad berserker guys who (of course, as Khornate) don't like Psykers
[] Emperors Children
Slaaneshi by default. With Noise Marines etc.
[] Thousand Sons
Tzeenchian by default. You would, of course, be basically just a bunch of Chaos Sorcerors and Rubric Marines.
[] Iron Warriors
VEHICLE GUYS. Technically Chaos undivided, but really obsessive about vehicles. Oh, and they have some special connection to Obliterators.
[] Night Lords
SNEAKY SNEAK. Terror tactics and apparently they don't like summoning demons?
[] Word Bearers
Strict Chaos Undivided, with organized religion, with their own EVIL CHAPLAINS AKA Black Apostles.
[] Death Guard
Nurgle guys. I am not aware of them having anything really other than that.