As fas as I remember the different Owen Paris was seen only one time. Richard Herd had more to do to fill the role and is therefore rather linked with Paris than the other actor.
Even the Borg Queen was played by different actresses...
Once again,
Lynx to the rescue to explain a strange event in the sometimes rather weird Trek universe!
As we could see, the Owen Paris who did show up in the later seasons didn't look the same as the Owen Paris we saw in the season 2 episode "Persistence Of Vision".
The reason for that is that the guy which was seen in the later episodes wasn't Owen Paris but a relative.
That was a result of the "Nick Locarno" affair.
Nick Locarno was the result of an affair between Owen Paris an a woman named Esmeralda Locarno who was not his wife.
Owen Paris tried to keep the whole thing a secret. He helped Nick to join the Academy. It was when Tom found out about this, he really started to hate his father.
When Nick screwed up and was kicked out of the Academy, Owen Paris continued to cover up his involvement in the affair.
In later years, Owen could not stand it any longer and got a nervous breakdown. During his absence and due to the fact that Starfleet Headquarters wanted to cover up everything that had been going on for a long time, Owen's brother Ichabod Paris served as his "stand in" at Starfleet Headquarters until Owen was well enough to return to his job.
So the guy who showed up as Admiral Paris in the later episodes was Ichabod Paris.
As for the Borg Queen, the first one was overthrown, turned into a drone, eaten by the other Borg or whatsoever because she disgraced herself by wimping around Picard like a lovesick schoolgirk in "Firts Contact" and the other Borg Queen took over.
