For me Space Feudalism is Da Way.
Somewhere between Fading Suns, Dune and Warhammer.
Bit more diverse and larger than FS with its (5 houses, 5 sects, 5 guilds standard), less sprawling and less based on SUPERHUMAN than Dune, less insane and parodistic than 40k.
Both psionic and some occult/theurgic/mystic more organised powers are fine for me. Diversity of weaponry.
Some sort of anti-technology stance as common tendency among mankind at least default mankind.
Definitely space demons.
Aliens both somehow humanoid - potentially linked by common meddling of ELDER RACE, and alien from world independent from ER meddlings.
Not much massive bombastic wars like in 40k. If such happens they fuck up whole civilisation for few generation.
Now one thing in those 3 that always annoyed me was some future space religions that payed symbolic structural lip service to real life Abrahamic religions while being fundamentally something else - Ecclesia in Warhammer, Church in Dune. I decided way to avoid this sense of irkness would be to remove abrahamic religions from backstory - evolve world independently from Year 0 (one would say even earlier but I think generally speaking Israel was geopolitically one plucky Caanan kingdom among many, and never had like reallly imperial role in history sans religio) and then like move humanity from pagan philosophies of imperial era, to religion based on revelation while in space.