For #1, you can have a monorepo setup where all your packages are local with a root rescript.json, v12 built-in build system handles it out of the box.
I think you’ll then need to install and set up all the packages in rescript.json, so not always ideal, but can be very convenient for more modular/granular coverage.
I think rescript-mui is a pretty good example of such monorepos.