Ineke I have a funny story about bettas and shrimp. Last time I had tanks I had a few bettas and some cherries. I was under the impression that bettas would definitely eat shrimp, so I kept them separated. (They certainly chowed down on my ramshorns!). Anyway, I was trying to breed my cherries for stronger colour and reluctantly decided that culling the cherries that were clear would best be done by feeding them to the bettas. I know a lot of breeders feed their fish culls to oscars etc.
So I braced myself and put the clearest in with one of my betta males, and hurried away so I didn't have to watch the horrifying scene unfold. When I was doing my nightly check on my tanks, I saw the cherry happily feeding on the moss and the betta ignoring it completely. They lived together after that. So much for culling! The whole process was so distressing I decided I didn't have the heart for that type of culling anyway.
I used to feed mine wrigglers and daphnia, they loved it. You're right about their personalities, they do learn to recognise different humans and they can be so engaging.