Until they are the lone dominant rooster in the flock, you cannot be sure how they will behave. I hate to say it, but their attitude and behavior can change if they no longer have a dominant rooster to keep them under control. If you can tell which one is dominant and he meets your standards, I'd suggest keeping him. If you see one that does not meet your standards, even with a dominant rooster around, you do not want to keep him.
An adolescent rooster will have supercharged hormones when puberty hits. Most of them will want to mate anything in site. It can get pretty rough, especially since the girls usually don't want to cooperate. Most, not all but most, calm down as they mature and learn some control. As long as they are not physically injuring the girls, this is normal and natural, but it can be distressing to watch, especially if you are not familiar with the process.
A rooster has two prime directives, protect the flock and make sure all eggs are fertile. Hopefully yours will never have to give his life to defend his flock, but he will if called upon. Chicken mating can look rough. It is not unusual for the hen to resist or at least try to run away. If you think mating when the hen is not injured is bullying, you don't need a rooster. All roosters are going to try to mate with the hens a lot, and many hens will try to run away. To me, that is not bullying. It is following his instincts. Some roosters are brutes and don't need to be kept around. Some hens are brutes and don't need to be kept around. I've gotten rid of roosters and hens because of their behavior. There are a lot of good roosters out there. I hope you get a good one.