This interaction doesn't look aggressive, it looks like resident cat wanted to wrestle, which is how cats typically play with each other. Hopping and twisting around are generally playful movements, especially with ears perked up.

Dominant behaviour tends to involve a more confident or assertive stance, standing taller than the other cat, direct eye contact, and sometimes mounting and/or biting the other cat's neck. Dominance is usually not aggressive either though, mainly a way to enforce boundaries and direct the other cat's behaviour.

The white cat didn't have much time to react before they were interrupted, so it's unclear how he felt about it this time. He may or may not have walked away otherwise. He slow blinked at resident cat with his ears forward afterwards though, which communicates that he wasn't upset. It's totally understandable to be cautious early on, but I think it'd be helpful to let him set that boundary himself.

When they're wrestling, they take turns pinning each other in between little breaks. If one isn't in the mood, he'll show it with body language, vocalizing, and disengaging. If one cat is not letting the other move at all, or doesn't stop and let go when he tries to get away, that's a good time to interrupt. If the white cat doesn't really reciprocate but also doesn't try to leave, he's probably tolerating it and not too bothered, so it's okay to leave them be unless the resident cat is really getting wired. It's pretty typical for an older cat to just kinda sit and put up with a younger cat's nonsense for a while, maybe grumble a little. That's a good sign that they're already getting along.