At first I was thinking of making my 10G a betta tank, but then I saw endlers and now I can’t decide. In the case that I do go the Endler route, though, how many could I house in a heavily planted 10G? What’s the male to female ratio? Could I keep all males if I didn’t want babies?
I'd go with all males in a ten unless you have a plan for fry. I've done all males in a 10 gallon before, they would posture and and chase each other but never caused any real harm. You could probably do 6-10.