With USUK, do you think there'd be any big diffrences in its dynamics and kinks if its Amelia x Arthur or Alfred x Arthur?
Oh anon, the short answer is yes.
The long answer is that first of all Arthur generally treats men different than women and of course that difference is present in these ships.
Arthur sees himself as a gentleman and he does act like one when he's allowed to (more like allows himself to/doesn't let his emotions boil over). Classic gentlemanly behavious includes being the guy who treats a woman like a queen so towards Amelia he is respectful, considers her every wish and pleasure with his actions and (and this is the cruicial part for me!!) willingly lets her take the lead if that is what she desires. Particularly with a woman like Amelia who is headstrong, knows exactly what she wants and needs and isn't shy to articulate it, even a man like Arthur, who is usually confident in his role as the dominant partner, can let his inhibitions go and comfortably submit to her.
She's the mommy type, wants to please and nurish her partner. A gentle mommy "dom" - though not particularly dominant. She doesn't have to be as Arthur naturally relaxes into her and lets her take care of him and his (sexual) needs.
If you want to know more about how I see Amelia and Arthur's sexual relationship you should check out the endless trust AU tag, cause I basically have an AU revolving around how they explore the kinky parts of their relationship. Cw for age play/agre regression/pet play though.
Now Alfred and Arthur, I have so many different version of them and some of them dabble into very hardcore kinks, but I'll behave for this lol. What's important about their relationship to me is that Alfred is young and eager while Arthur is more experienced and refined in his technique - and this goes for pretty much every situation they are in, be it work, dinner, or sex.
With Alfred I always let canon play more into my headcanons than with Amelia which means Arthur has learned to keep his possessiveness under control, but given the chance, he can and will let Alfred feel that he is his and no one else's to touch. This can be through tying him up, making him repeat who he belongs to over and over again while barely being able to speak while his prostate is hit again and again. Alfred doesn't really care either, he's a people pleaser with an oral fixation and he gets off on doing whatever Arthur wants him to do.
Alfred's main kink is servitude + whatever Arthur is into. Which is. Most things. I love to play the Erotic Ambassador Card to remind people of Arthur's canon status as a perv, because that's exactly what he is - horny and unashamed. He gets off on embarassing Alfred too, teasing him and putting a hand on his butt in public, pulling him in a heated kiss in the middle of a crowd. It's yet another way how Arthur can show off his ownership of Alfred.
Okay I digress a little, I'm sorry. tldr Amelia mommy dom with her baby/pet Arthur. She fucks him with a strap sometimes. Experienced dom Arthur x eager virgin Alfred who is willing to indulge in every kink Arthur presents him with.
