I obviously agree bristlenose can be kept in a 10g (unless you don't plan on supplementing their diet, then they need more space). They need surfaces to shuffle along more than they need swimming space, so a 10 g with lots of broad-leafed plants, rock, etc. works IMO.
Most of my bettas have been homicidal toward the zebra danios, so just based on my experience I wouldn't try them with tetras. My bettas have all hunted my shrimp, but the gouramis were the killers.
And just to be clear, I wasn't recommending gouramis with bettas! I was just trying to give an idea of the bioload a sponge filter can support. Although mine do get along swimmingly ( HAR HAR HAR). I only moved the betta there because I feared for her in another tank, and they've been completely indifferent to one another. Now, inter-gourami relations aren't as smooth, but there is never any damage to anyone.