I don't have direct experience with bettas, but I've never heard that pairs will work long-term in any male/female combination. There's research that suggests they prefer to be alone or in large groups, rather than with one other fish. From Social partner preferences of male and female fighting fish (Betta splendens), by J.L. Snekser, S.P. McRobert, and E.D. Clotfelter in Behavioural Processes:
Despite high levels of conspecific aggression by both sexes (e.g.
Goldstein, 1975 and Jaroensutasinee and Jaroensutasinee, 2001b), in
most situations Betta chose to spend significantly more time with
other fish rather than swimming on the empty side of the test tank.
Two exceptions to this general preference were seen: males did not
spend significantly more time with a single female test fish and
females chose to spend significantly more time on the side of the test
chamber that was empty than spend time with the single male fish.
In other words, lone females went out of their way to avoid lone males, and lone males didn't seem to care much one way or the other about lone females. A pair of males was found to be the most aggressive combination.
The paper also mentions that, in the wild, you'll find about 1.7 bettas per square meter. And that's in the wild: remember most domestic bettas have been bred for aggression and are probably even less tolerant of their neighbors. A typical 30 gallon has a 0.27 square meter footprint (91cm by 30cm), so I'd say that's not enough room for a pair to establish their own territories. (I'm not personally sure if the females are territorial, but if not they probably prefer to avoid a male's territory when they're not breeding.)
As for compatibility with neons, nothing I've heard makes me think it won't work unless you have a really aggressive male. That many tetras should feel safe in their shoal, so I wouldn't expect to see much fin-nipping from them; and 30 gallons planted means they won't constantly be in the betta's personal space. And the bioload from this community would be perfectly safe for this size tank. One thing I'd suggest you check though, if you haven't already, would be water parameters: neons tend to live in cooler waters than what I've heard about bettas. You might find cardinal tetras a better fit if the bettas need more than say 75 degrees F or so.