Migrate from GWT to JS frameworks

I have a JS library that is embedded into multiple other websites.
This library creates

1. Widgets (like the usual chat widget seen on multiple apps). These widgets are primarily iFrames
2. Also it monitors the application state to show certain messages to users on certain actions. This is primarily logic that listens
   to events on page, tracks all mutations etc.

This library is entirely coded in GWT. Facing problems in retaining and hiring FrontEnd developers to work in Java.
Thinking of moving to React for widgets and Typescript for logic.
Queries:

1. Is React + Typescript a good choice ? I evaluated Vue, Svelte. Are there any other frameworks/libraries that can be considered ?
   [Note that this library sits on top of multiple websites built in variety of ways. Primary requirement is to avoid any kind of javascript namespace conflicts]

2. For widgets where most of the logic is UI related, and which are restricted to iFrames, we are thinking of rewriting the code in React. Is there something else we can do ?

3. For logic(where there is no UI related code) , is there a way I can directly convert all GWT code to human readable and maintainable Typescript at once ?

4. Any other way to undertake this overall migration ?