Hi Josh,
Wild betta's are found in rice field's. The closest you would want to come is natrual substrate suchas small stones & a planted tank.
Angelfish can't be with bettas because of the finnage. A betta would probably make short work of your poor angels.
Male & Female betta's should never be kept long term together.
Female bettas should only be mixed with a male while breeding/After they have embraced the female should be taken immediatly from the tank/males take care of the nest.
Ideal temp's should be 74-80F
If it were me I'd use the 20gal for the angel's and find another community tank for several female bettas along with say some umm Mollies
And if you go with the male a 2-5 gallon for one male and maybe a Dwarf frog.
This is only my personal opinion. I have 2 guys presently in seperate tanks & a 10 gal. molly tank w/fry
Oh just a thought.. You can also use a divider to keep 2 or 3 males in a 10 gal. Looks pretty good with plants at the divider's to keep the boys from flaring at each other all the time.
Okay sorry for the book.. Keep me posted on what you decide Good Luck