Yes, bettas are really smart and each have individual personalities. Bettas and corydoras catfish seem to be a good match. The cories will not bother the betta, but if you have an especially aggressive betta they might pick on the cories.
Also, a tank of female bettas can work, but there are instances where it may not (overly aggressive females for example). So, before you decide to do a setup like that I would recommend that you research the topic and decide whether you are willing to put the effort in to offset the risks (there is no guarantee though either way).