If all goes south I have two tanks for themI have three communities with bettas, these temporary communities that house growing out bettas that I’ve raised.
36gal with plecos, young angels, one male betta.
36gal with rainbows, plecos, rasboras, snails and one malebetta
20gal growout with female bettas, BN plecos and a pair of brevis shell dwellers (temporary).
I think female guppies will be fine with a betta provided the betta is well behaved, the tank is at least 20gals and is well planted. I’ve only had 3 overly aggressive bettas that could not get along in a community setting.