I'm not sure how angular works and pretty noob with Vue but IIRC yeah Vue works in a way that it modifies the existing template, so indeed I agree that's a recipe for disaster in this case.

With React (at least the way I use it in those cases) is that my main Rails template only renders an empty div container with props for React to render in it. So my full rendering is handled by React, so there is no mix up between Rails and React with data/rendering.