Males with large finnage get stressed patrolling because they've been bred to have unnaturally huge fins, which weigh them down and put an immense stress on their bodies. I've seen OHMs with fins so big they swim at an angle because they're so weighed down - its depressing.
"Seeing them in action" wouldn't be anything pleasant... in action for bettas means ripping one another apart, and it really isn't fair to let your fish harm one another like that just for entertainment or curiosity. My suggestion would be to buy a group of related females from a breeder, or a single male Plakat (they have small fins and would do fine) - but only if the other fish in the tank are peaceful, not fin nippers, and have no bright colors, or you'll either have hurt bettas or hurt community fish.
Like I said, a tank that large and tankmates are both far from the ideal for bettas, males especially, so you might want to consider what is best for the fish. Females are probably a better bet since they are less territorial and a little more passive, and you can find them in very lovely colors if you're thinking of buying from a breeder.