So far I have a white opal Betta I got from Petco and 2 golden back shrimp 1 orange Sakura shrimp and 2 ghost shrimp. I’d like to get 6 harlequin Rasboras or Rasboras of some kind and 5 more shrimp. Would this be okay in a 10 gallon tank?
In terms of the tank, yes that is fine...but I do see some issues. Bettas will hunt and eat shrimp. Yes, some people report short term success, or have enough plants that the shrimp can hide well enough to get by, but in the end, bettas are predators and shrimp are snacks.
Second--mixing different color varieties of the same species of shrimp results in the color lines breeding together and you lose the original. Different species of shrimp have different water chemistry needs, so mixing across species isn't recommended. Right now you have N. davidi and N. heteropoda, (excluding the ghost shrimp, they won't cross). You will have better luck putting in more of the same rather than adding a third, or moving them to their own setups where you will see much better reproduction success as well as activity.