I have been needing to make slightly more complex Bela GUIs than
p5.js is appropriate for, and have been experimenting with the Svelte framework since it's designed to be highly "reactive" and scalable.
I have forked their template app here and wrapped
Bela.js into a Svelte store
Svelte has tutorials, examples and a REPL on their main page: http://svelte.dev
And here's a tech talk about the thinking behind it: