If you're going focus mobile app, web is just nice to have, I would suggest use native (Swift/Kotlin,Java) to build your app, it may take some time at the beginning, but it'd save a lot of your time on dealing verity of issues (like setup Payment, Notification)。
I'm building a blogging, journal app (https://giki.app) and it's using React native, it got up and running very quickly at beginning util I need enable in app purchase.
Your guys are so right about fx’s ‘Poor man’s README, I will update it soon. Long story short, you can deploy fx on a host (cloud or localhost), then you can deploy a function to be a service in few seconds, just like AWS lambda ( but Poor man’s lambda).
README is not quiet clear, but for my understanding, lambda is kinda thing that helps you to do serverless, but lambda is also running on some kind of server maintained by AWS, right? fx is kind of lambda, but owned by yourself.