if you want fast web pages there’s nothing faster than pure CSS and HTML. those are both running native machine code in the Web browser directly.
JavaScript (with or without frameworks) gets slower the more things you do with it as it only works in a single event loop. this means one function you wrote that takes a long time blocks everything else from finishing until it completes, even the browser rendering and interactions. that’s why really bloated pages feel like they’re lagging and you can’t click buttons or scroll.
imo do as much in CSS and HTML and use native web components for reusable components that you can drop anywhere in your HTML. if you want it to feel like an application, since you have backend experience you could use web assembly but treat this as a single application, it’s not really meant to replace html/JavaScript
kwin supports this, gnome from my perspective is more about a cohesive experience you either love or don’t