What would I use? Standard tech stack: React+Apollo+Redux+GraphQL (with Typescript). React Native for mobile. On the backend, Postgres DB at first, upgrade to CockroachDB or something when needing scale. Choice of language for application server to translate GraphQL queries to and from SQL queries is the only thing I would be unsure about - either Python or Typescript probably.
But this is because I'm very familiar with these frameworks. Productivity using them is really high once you've learned them well. But the learning curve to learn these technologies might be more than the amount of work that goes into making a Google Keep clone with a more approachable framework...
Nearly all the new startups I interviewed with recently were using that stack, except some had vanilla JS or were only partially converted to TypeScript.
It's becoming the de facto standard stack for new projects.
No particular reason other than I'm used to redux.
My gut reaction when it came out was "it seems rather unwieldy compared to
redux to have to manage client-side application state through graphql", but my gut reaction could be wrong, and I haven't actually tried apollo-link-state so this isn't really an informed opinion. Notably though, it feels think graphql is great for graph data, but pointless overkill for most global application state which isn't really graph data.
But this is because I'm very familiar with these frameworks. Productivity using them is really high once you've learned them well. But the learning curve to learn these technologies might be more than the amount of work that goes into making a Google Keep clone with a more approachable framework...