> I'd put network use in a different category. It is an important issue though.

My rationale for considering it to be included is that as the concept was developed I took the spirit of progressive enhancement to be doing the best with what your users have rather than only catering to people with the same setup you have.

> Now I just wish more devs would start to take advantage of all the great performance tools available. Those best practices are unfortunately rarely taught.

Agreed. I think one of the challenges has been both showing business value from performance — once you're putting things into a cost/benefit comparison it's a lot easier to get people to routinely consider the performance impact of their decisions.

for font-display, do you prefer swap or fallback?

It might depend on main body text versus title text. It's jarring when body text changes so I'd prefer fallback in that case. For a title which might have more branding concerns, I'd prefer swap.