Bettas are big on personality and intelligence in general. I've had some chill bettas who've shared a ten gallon tank with shrimp, and ones who have eaten all the shrimp in a couple days. Some ignored the other fish in the tank, and one had to be put in his own 5 gallon tank because he would chase everyone and stress himself out.
My favorite betta would refuse to eat the pellets I got him unless I ground them up into smaller pieces with a mortar and pestle. He totally could, he just didn't like to. Once he found that I would break them up into smaller pieces for him because I didn't want him to starve, he stopped responding at all to whole pellets and would stare and wait for me to grind them up before swimming to the surface. "Pardonnez moi, mademoiselle, these are unacceptable"