I think Kirk's threesome could've been cut from the film. I think it's a caricature of Kirk to say he would do something like that.
I have no problem with Kirk having sex with two beautiful women, especially at his age. Maybe TOS Kirk would have a little whisper in his head saying "be discreet" and maybe.. he wouldn't. And maybe in this century enjoying yourself in bed with some tail (SEE WHAT I DID THERE) is not "something like that" but just mutual recreation.
I agree with you that Carol's underwear scene is gratuitous. I think showing Zoe's ass was another faux pas. It's not perfect, but the character of Uhura is 10x better than any woman in Starfleet before her. It's just not to where it needs to be outside the Star Trek world.
When did they show Zoe's ass?
And yes, gratuitous underwear. I would have preferred to see her in bed with someone if they wanted to flash her underwear. But whatever. I think we're getting some foreshadowing for Kirk's future relationship with her.