A Typescript LSP will catch a ton of js errors for you, even if you’re not doing ts.
There is a plugin for the browser and the Atom editor called Emmet Livestyle. It’s the only real time preview plugin I have ever found. And I don’t mean reload on save - it would update the loaded page html/css in place with your changes as you typed them. I don’t think it was ported to vscode unfortunately.
I have also fallen in love with the lit-html library.