So I've tried short games with different origins:
Poachers - if you start by getting some more poachers and random cheap spear+shield men this might be the smoothest early game I've seen. 5-6 archers plus some random militia/farmers in the first line completely wreck bandits, thralls, goblins without lots of wolfs and low-mid numbers of beasts but predictably sucks vs undead (it's real easy to snipe necromancers though). I haven't fought orcs, which would also be hard once they get warriors. Nowadays I mostly build archers as dedicated ranged support without polearms but here it might be necessary to have a backup weapon on everyone because bows just don't have enough power vs tanky armored enemies. I think there's a lot of potential here. Not sure how you'd handle mass ancient dead or nercosavants though, other than just having a large specialized reserve.
Deserters - after trying this one out a couple of times I think deserters might have the absolute worst cost/stats ratio in the game. Not only do they often have sub-20 base resolve which makes their high melee def completely wasted once they engage the enemy and start running, but they seem to have more bad traits than any background other than cripples and beggars. I don't normally restart unless the map seed is completely fucked but here I had multiple starts with craven, clumsy, dastard and asthmatic on 2 or all 3 starting men. I hired some more deserters but they also had lots of bad traits (one with iron lungs though) and for that cost you can do much better with militia and retried soldiers. My one not-terrible start was cut around day 15 because a noble house unit ambushed me in the forest outside their territory. Oh well. You can raid caravans from your former house for some easy loot. You could maybe make something out of it with a good sergeant and a banner but feels like an uphill battle with no upsides.
Beast hunters - doesn't really feel unique in any way other than you get worse prices. Bonus loot from beasts is very contract-dependent because running around woods chasing wolfs and spiders doesn't pay and there are no beast lairs to pillage (why aren't there beast lairs?). You are not actually better at fighting beasts in any way either. Meh.
Cultists - interesting but gimmicky. If only there was a more reliable way to get more cultists or attempt conversion of other backgrounds.
Lone Wolf - very strong as long as you don't actually fight as a lone wolf but slowly build a small squad of mid-high tier bros.
Raiders - like deserters, but good and fun. The only problem is that it's hard to get more barbarian recruits or gear.
I haven't tried the legends mod yet, I'll probably do when they slow down patching the game and the mod hits a more stable version. A lot of it sounds like a mess (wizards, backgrounds increasing map move speed, camping autism) but then I read
Save your troops into formations to prepare for different battles
Assign anyone to reserves, but they are forced to fight if you're attacked
Different backgrounds can have unique perk trees with entirely different abilities
Ingame sliders to control world size cities, factions, oceans, forrests, swamps (experimental, read the tooltips)
6 new AI Noble house archetypes
Tryout when hiring now reveals stars on attributes
And these seem like they should be added to the base game. Camping stuff might be cool too if they did it right.