IIRC Takei wasn't 100% for Sulu being gay in Beyond because Gene wrote him to be straight. But I don't remember if that was true or taken out of context.
Takei's objections to Sulu being gay in Beyond are related to an interview he did in 2005/2006, shortly after he publicly came out where he was asked about Sulu's orientation, and he said he's always viewed Sulu as a straight man, and by making Sulu gay, he felt his wishes were being ignored. That said, however, Indeed. The only time in TOS Sulu showed any interest in women was in the Mirror Universe. And even then, Mirror Sulu to me seemed to be acting too straight, meaning he seemed to be overcompensating to cover his homosexuality.
Well, you got me there. I take no shame in admitting I've watched Mirror Mirror more times than I've watched The Way to Eden.
His feigned interest in Uhura was his beard... ...Not to be confused with Mirror Spock's actual beard, which was just a beard.
My guess is that they only exist in the past, as time remnants of some sort, relics from a previous iteration of the timeline, that left physical imprints on the timeline during their travels, but who's future existance no longer exists. They would be in the past as residue, clueless to any of it, and would blink out of existence as they time travel back. Since this precludes the ability of Gracie and George going to the current 23rd century, I would assume that the Federation must find a new way to deal with the whale probe, or find a new source of whales. The question in your post, IMO, is applicable to any situation wherein outsiders from the current iteration of the 23rd century *also* travel back to those events, and unintentionally interact with their previous selves. If Pine-Kirk or Peck-Spock end up looking for whales in '86 SF, for instance, and diverted our original Shatner/Nimoy remnants from their paths, causing new butterfly effects to create yet another new iteration of the future (similar to whatever the current one at the time was), then they theoretically could all return to the new "top layer" timeline together.
Pretty standard timeline rewrite, subtle, similar to the original one, because the addition made no major butterflies until the progeny was grown. We don't know what the lack of Sela would have done to the timeline; it was a previous interation (without her) that went unseen (we don't know what a sela-less post Yesterdays Enterprise timeline would look like, because we hadn't gotten to view past that point yet.)
The weight of the universe increased by a few hundred people, which means that the universe will expire a few millionths of a second earlier.
Its the Mirror unvierse they don't use labels, as long as your partner is human you can sex anyone. They are Terransexual. Or a clone like Baby Tucker
Or created through artificial insemination, surrogacy or superscience that combines genetic material from both parents.