I’m biased as one of the authors of Y-Sweet, but I think Jake’s choice of Yjs + Y-Sweet is as good as any to start with. We’ve worked a lot at making the localhost environment easy to get started with, and Yjs is the de facto CRDT with the most written about it.
I'd like to start with something that's more DB oriented like SQLite both locally and in the browser for example but I understand a documented-oriented approach might make more sense.