The only time i wondered if Regina was like the High Queen was because in Ep 3 Snow and Charming were talking about the evil fairy dust and Snow says she has it saved for someone special. And Charming says who ah the queen or something. It was like she was The Queen and he didn’t refer to her specifically. That made me wonder if Charming’s kingdom was under Regina’s which is really Snow’s kingdom. Though in context he is, of course, talking about Snow’s Evil Queen, but it seemed a little strange. Though in later episodes they implied that Midas would overrun Charming’s kingdom unless they became allies through the marriage which makes me think that Charming’s kingdom is not under the Queen’s because i don’t think she would allow that. Though she may allow squabbling like that.
I don’t know. I still think of them as separate city state kingdoms until we get more information.