Bettas aka Siamese fighting fish were bred for aggression for many many generation before they started to be bred as pets. The aggressive/territorial streak is still in them, both males and females. Some its much more apparently than others. Planning a community with a betta you must:
1: always be vigilant and observant of an signs of things going wrong. Just because the fish is behaved for first day.. we.. month doesn't mean it won't turn and attack tank mates in a year.
2: always have a backup tank ready to separate betta from its tank mates (this means having a spare heater and ideally a cycled filter as well). Worst case you can put the Betta in a breeder basket/net on the tank but this shouldn't be long term-make sure it has a lid of some sort or the Betta can hop right back into the tank to terrorize some more.
Sororities
I'd strongly advise against sororities. They take a very very densely planted/decorated tank for tons of line of sight break up (i mean you cannot see from front to back of tank, nor see the side wall glass from the other side). Minimum 4-5 girls in a 10g, but same thing again, there can be violence right off the bat as some girls just aren't good for sorority life.. some may snap in a month or year and the tank turns into a was zone with corpses. If one gets sicks it can upset the hierarchy and start fights for new dominance which against can lead to a dead fish... unless the owner takes the sorority apart, these tend to end in disaster eventually (sometimes sooner than later).
Shrimp
Well bettas are predators and shrimp are just lobsters to them.. they'll likely be on the menu. I tried keeping larger shrimp species (ghost and amano) with one of my bettas, he killed them in the first day each time I tried putting them in. I watched him guard and pick at a kill for a while before removing the body... On the other had I put in some cherry shrimp in with my most timid betta and the adults have lived ok, he doesn't put out much effort hunting them. But I never see shrimplets (even though I know I've had berried females) so I'm guessing he gets them. An extremely densely planted tank, that's been cycled and aged (running with plants) for 4+ months is recommended for first time shrimp so ensure plenty of natural food has grown in the tank for the shrimp. Just be mindful getting shrimp might mean an expensive snack for your betta, especially a female as their shorter fins (along with plakat males) make them petty fast so they have a better chance of catching shrimp.
Snail
Again depends on betta temperament. I've seen some tanks where betas get along fine with a mystery or nerite snail.. I've also heard fro owners of bettas eating eyes and antenna, and even picking up and throwing snails against the tank wall repeatedly(grabbing by body when out). I tried putting a nerite (normal residence a 55g) in my oldest bettas' tank to deal with some diatoms.. next day he was dead ad my betta was a bit fatter...this betta seems to know how to eat trap door snails, he's also eaten MTS.
Other fish
First you need to research the species you're considering. Not all fish are compatible temp/temperament wise. With other fish you have to be mindful of betta harassing them, or them harassing the betta (nipping fins etc) including fish like tetra (seems to be worst when not in proepr school sizes but can still occur in larger groups).. Don't do danios or white clouds-danios are way to fast and nippy(and imo need much bigger tank than 10g), white clouds are cold water fish. Dwarf or pgymy cory would be best option for a 10g, other cory species need larger tanks. Be mindful of the betta harassing/nipping them though. I've read of some betta owners who's cory have no dorsal fin from their betta being aggressive.
