I can totally empathize with the large form woes, having worked on a couple of similar client projects with similarly unusual requirements. Angular (the first version, I hear awesome things about the latest), in particular, fell down hard when managing a very large number of semi-dependent input fields. We ended up customizing large swaths of its collection diffing code to gain minor performance increases before designing a pure JS solution that was very performant, if very expensive and time-consuming to implement. I have no reason to think that React would have fared any better in either case.