Hi
I have 3 Amano Shrimp with my male Betta in a 20 L tank (5 US Gallons). He completely ignores them, even when they swim to the surface to steal his food, they also sneak up on him trying to take things away while he is resting. He really doesn't seem to notice them. (or chooses to ignore them) lol.
On the subject of Corys and Otos. I have both, mine are not in the same tank as Aslan, (My Betta).
Corys/Otos will be in their own world and not really pay any attention to the Betta's (as long as they are comfortable with their presence). I would be careful though as if you have 4 females in the tank already, adding more fish may take you over the limit.
I have 4 Bronze Corys in my main community tank, and they are very active, and I think, similar to Albinos's but would not be suitable for a 10 Gallon, with a Betta or Bettas (IMO).
Pygmy Corys could work, but they are so tiny, and I have found, quite sensitive to water conditions. You could try them, if you have a back up plan. they do love sandy substrate, but unlike some Corys spend alot of time swimming about in the mid/upper levels of the tank).
I don't have female Betta's (yet)

and I know they are more "community friendly" than the males, so maybe my advice is not entirely accurate. Hope this helps though.
Amano Shrimps are really cool. Can't recommend them enough, best Algae/stuff cleaners ever & amazing to watch (and a fair bit bigger than Cherry Shrimp, so not so vulnerable). They also have a low bioload which is good. (as long as they have somewhere to hide away, if they feel the need).