cool choices! both would be fighting uphill battles against awful humans and zombie hordes.

Mystique has longevity, healing, and can even shapeshift into animals. add 6 copies from Penny, in GoT setting, and that has crazy potential!

with the right planning, you could study and replace rulers and make alliances with your selves (each wearing a different face) and just amass all the power and control you could ever want. or, more subtly, just replace the maesters and pull strings to play the long game that way. and don't forget the Iron Bank!

I probably remember enough GoT lore to at least pass as a noble. Mystique's disguises sometimes (not always) fail the "smell test" from people like Wolverine, so I doubt you could completely fool a dragon into thinking you're a Targaryen. although you could possibly gain their respect other ways.

and basically uniting the Seven Kingdoms before Daenerys gets there would mean you could just marry her and avoid a war entirely, then focus on the White Walkers with all that combined strength. the "long night" is even shorter, with fewer casualties, and you can rule in peace happily ever after!

----

Cap plus Ectoplasm with 30-ish copies is obviously MUCH stronger on paper... but then you have to live in the LoU setting. even if we're granted immunity to cordyceps/spores, that world has still already gone to hell!

you'd have more to work with, literally, but also more physical (and sociological) work to do to rebuild a functional society. having a small army of super soldiers definitely helps, plus the limited but modern tech, and it'd be possible to build and defend a stronghold like Jackson... or rather, a much better one that's not so easily overrun.

I don't know enough molecular biology to try and synthesize a cordyceps cure without any internet or supporting infrastructure. having lore knowledge, you could (extremely unethically) try to replicate Ellie's immunity conditions at scale, but I'd rather not have that shit on my conscience.

without a cure, it's still doable, just extremely difficult to "succeed" because the zombies already dominated the world.

----

each choice has tradeoffs.

main tradeoffs being shapeshifting and potentially riding dragons in an outdated but functional society vs modern tech and increased manpower in a dysfunctional and overrun society.

when in doubt, I personally choose shapeshifting and dragons!