... presumably it would 'break' basically all of them, given that this is a remaster, aka, a different game, the same way that the GTA Definitive editions are remasters of the original games.

The Creation Engine is now ... what, 15 years older?

And if they do what they did with the Oblivion remaster, it'll be a frankenstein of UE5 and the Creation Engine.

So yeah, you'd have to make all the mods all over again, perhaps with a few very rare exceptions...

But it wouldn't break the original FONV.

... Unless they just decide to do that also, like they did with FO4.

... Also FONV works fine now, modders have fixed and expanded it greatly.

https://vivanewvegas.moddinglinked.com/