I’m still using app passwords which seem to be working for me. Did they stop working for you for some reason?

What is the difference between the vanilla and GNU versions?

I’d start by configuring an incremental completion framework. This is the single best feature of Emacs and its packages IMO.

You want to keep things simple, fido-vertical-mode is built-in and is already a big improvement over the default completion.

If you want something more powerful, the vertico-corfu-marginalia-orderless-embark-consult completion stack is the best currently available IMO. However, something like helm or ivy is also an option if you don’t want to install a ton of packages.

I haven’t usedlsp-mode with JavaScript. However, the first thing to try is to check if there is an alternative server that might be faster. This makes a big difference for some languages.