The "somewhat archaic" standard of beauty on Barrayar, the one that Miles and Aral share, is the "squishes nicely" ability to survive a small famine. That's going out, as Barrayar's catching up to the rest of the civilized wormhole nexus, and has reliable food supplies, and modern medicine. "Squishes nicely" would enable one to survive a disease that involves not being able to hang onto food for long, as well as famine.
Beta Colony has gene-cleaning, so I should think that two things would happen there, as far as beauty goes.
First, greater-than-natural symmetry of feature would be achieved, as said onlist, and thus the bar would be raised. If you've got merely good bone structure, as opposed to perfect bone structure, you'd be quite plain by comparison.
Second, possibly not mentioned onlist, some physical attributes that might once have been an external marker of undesirable hidden genetic traits could be expressed without the actual flaw. Say, an eye color that's commonly linked with blindness? On Barrayar, that would be a dead giveaway that someone was a mutie. On Beta Colony, it could be a rare and beautiful trait. That could cause some clashes.
Beta Colony sounds, from all the body-modification bits, like it's a place where people can be comfortable with their body's natural balances, and if they don't like the one they were born with, they can jolly well change it. I honestly see it as having gone through all the "Okay, thin is in -- woops, not anymore, curvy is groovy -- woops, that's so last season, jack up your metabolisms again, boys and girls!" psychotic slaves-to-fashion mood swings some generations ago, and are now patiently waiting for the rest of the civilized world to catch up with them and just be themselves, the healthiest, happiest selves they can be.
Meanwhile, on Barrayar, beauty in body type is still a thing of fads. The Koudelka girls are being mildly catty about their sister's weight gain on Beta. (I read that as Kareen, freed from Barrayaran expectations on her, lets her body adjust itself to something comfortable for her.) This happens to be in fashion when she goes back, because the Empress-to-be is plump, and the beautiful-in-her-own-right Empress sets the body-type fashion for the rest of Barrayar.
Even on Beta, though, you're stuck with the face your genes gave you unless you go in for modifications. An inexpensive Betan facial mod might leave you looking too evened-out: see Michael Jackson or a store mannequin for the likely results. It takes a genius of surgery (and money) to come up with what Elli Quinn got: something that's still her, but with the minor imperfections tweaked from mild flaw into charm. Any Betan hack can probably leave you with Haut bone structure. It takes a really good one to leave you still looking like you.
I expect to see Barrayar doing fashion excesses for the next several generations -- first girls will start baring it all, and then there will be a swing back into covering everything they can, until it finally reaches some form of happy balance, probably with nods back to Barrayar's heritage.