I have kept males and females together in a 10 gallon aquarium..
My set up was a 10 gal aquarium with 1) bushy nose pleco max size 6'', 1) male VT betta, and 5) female VT bettas..
There was 6) female bettas but she was super aggresive and would fight as soon as she was in the aquarium. It just depends on how bad there attitude is.
Also as soon as I took the male out the females would start to fight a little here and there, The male betta kept all the females in check he ran the tank, and there was 5 of them so he never just picked on one. He had 5 to choose from so he would go at one then another one would catch his eye. So he never picked on one to where there tail got messed up. And as soon as the females would start to go at it a little bit he will run them off he will keep everything in control..... This is the only way I have been able to keep male and females..
I have raised spawns that had male and females grow up in 29 gallon and you just pick out the trouble makers here and there,, And thats had male and females in it and as the males reach adult hood you slowly have to take them out..
Pretty much some can be together and some not.. It all depends on the fish and how planted the tank is so theres places to hide..