Unfortunately the GWTP project hasn't been updated since 2018. I started using it but it was causing my system to default to use the 2.8.2 compiler instead of 2.9.0. I think there's a way to resolve this but it was just taking up too much time.
In the meantime I decided to do things a bit more manually with the idea that I'd migrate back to the annotation based style later once I had a better handle on how I wanted things to work.
Full compilation for my application with 2.9.0 isn't too bad. It takes about 43 seconds today from a clean GWT state (Java classes already compiled). It takes about 64 seconds from a completely clean state with a fresh Gradle daemon.
SuperDev compilation really saves me here. That still takes 43 seconds to start up, 12 seconds to do the first compile, and about 7 seconds to do the incremental compiles and that time generally drops a bit as I use it more.
MVP...
Model - my data types
View - displays the controls that the user sees and fires events based on user input
Presenter - does the actual logic on the models and handles events from the views