1. Doesn't matter so much as long as you're using newest versions of either one. Newest yarn has plugin support which is neat. Npm has more stable backing and an open roadmap. Could be some considerations regarding monorepo support, but otherwise either is fine.
I guess your point is that this would change constantly, which isn't really the case.
Yarn and NPM has been around for a long time. Yarn 1 used to be the better choice since NPM stagnated, now they're a bit more equal.
Typescript has been around for a long time. So has ES6 modules. Same for Jest and Mocha.
The only thing that is changing somewhat are the bundlers and build tools (thankfully, they've been the weakest part of FE dev for a long time).
I've kept up with frontend for many years. There really isn't all that much "fatigue" if one actually understands what the tools do and the niches they fill.
I agree with this persons answer, if your goal is to go full custom. If you want all this setup done for you I suggest NextJS. It should be noted that Deno is not a bundler but an entirely different JS Runtime. The question should be do I use Node or Deno.
1. Doesn't matter so much as long as you're using newest versions of either one. Newest yarn has plugin support which is neat. Npm has more stable backing and an open roadmap. Could be some considerations regarding monorepo support, but otherwise either is fine.
2. Yes
3. Use ES6 modules
4. Jest + Cypress
5. Vite