I'm stuck with macOS at work and these have also been the most painful parts of the experience for me. Luckily, I recently found Rectangle[0] and InstantSpaceSwitcher[1]. The former gives keyboard based arranging (though not focus; still just use cmd+tab for that) while the latter gives instant transitions between virtual desktops (including shortcuts for navigating directly to a target, rather than sliding over sequentially).
Lately I've been enjoying Open Props[0]. It's a library of CSS props/ variables that helps structure a design system. I like it because it's CSS-first, so like OP experienced moving off TW, I've learned more CSS, and it works with the browser not against it. It also provides some sane defaults for anyone less interested in fiddling with precise cosmetics.
Wanted to highlight MDN's HTTP caching guide[0] that OP links in the conclusion. It's written at a higher level than the underlying reference material and has been a great resource I've turned to several times in the last few years.
One note: I noticed when opening the installed PWA in airplane mode, styles didn't load. You might be interested in this article on PWA caching from MDN:
Goes over similar content as TFA, in perhaps a little more depth. Indispensable sysadmin knowledge.