I'm sorry that I didn't say bettas aren't good in community tanks earlier, I didn't see that you wanted one so I didnt say anything, and I am sorry for that.
I had Betta fish with neon tetras. Fine for about 5 months, then absolutely tore his fins apart causing him to die. I will not keep bettas with other fish anymore, but not because I'm worried about the small fish. Bettas can be pretty chill towards fish IME, but the small fish, especially tetras, will tear the bettas fins apart. Especially when they are in groups of 6 to 8, that will make them more stressed and prone to nipping. Also, bettas get stressed with other fish in their territory, even if it doesn't seem like it. Bettas are solitary fish in the wild, and I would only keep shrimp and snails with bettas.
If you saw "pictures" of Bettas as centerpiece fish, that doesn't mean that's it's going to work. I could see 50 pictures of a goldfish in a .5 gallon bowl and then go buy a goldfish for my bowl, but that doesn't mean it's right.
If a HAD to get a betta for a community tank, I'd go for a short-finned female. But it seems like you already have a male betta. is he a short finned or long fin better? I'm sorry to say but for me the only two options are either return him to the store or just keep it as a solo betta tank.You could add some shrimp and snails if you do keep him. Not sure about the otocinclis, as I don't have any experience with them.