I've only been keeping fish for about a month, so my advice may be incomplete or incorrect, however I have 3 rosy barbs in my 29 gallon. In your first video it appers that both are males, as everything I've read indicates that male rosy barbs have the "rosy" red coloring, whereas females have a noticeably different pale white coloring instead.
My 3 males have not shown any behavior as aggressive as your video shows, but I do have one that, from time to time, chases the other 2 around.
I considered getting more, but realized that rosy barbs are real tank busters because they get big. Sources I've seen suggest anywhere from 3 to 6 inches as an adult. That doesn't leave room for much else.
HTH