JS questions for a newbie

Hi, nice to see you here! Your way here is similar to mine :)

Just in case you didn't open it yet: https://forum.espruino.com/conversations/341830/#comment15028140

The tutorials linked on that thread are very helpful when starting out.

how important is it to a) create a scope in which all of my code sits so it can be unloaded correctly when I enter the launcher,

Not important. I'd almost advice against it to start with. What it does is allow fastloading, described here: https://www.espruino.com/Bangle.js+Fast+Load

b) avoid using 'const', and c) define functions via let, so that nothing is global and therefore (from what I'm understanding) still held in memory even when not in the clock app?

I would probably just go with using let for most things. If you want to you can learn about the difference of declaring variables with var, let and const (and declaring variables without any of them). But I mostly just go with let.

Looking forward to see your watch face!