I'd say 3 otos and 4-8 neons.
Or 3 otos, 4-5 neon, and a betta.
Could have a problem with the betta and neons.
I found out that I could have 6 cardinal tetras and 3 otos and My tank would be 99% stocked and I would have plenty of filtration.
I used this calculator: http://aqadvisor.com/AqAdvisor.php