Spring Boot. But that's because I don't mind big binaries, fastest to be productive(for me!), every tool is just another autoconfigured include...

I would consider trading these for faster build times... I heard good things about javalin.

I would definelty use Java. I like it and there are tonns of new features in the 11+ versions. Boilerplate is greatly reduced by Lombok.

I would consider Kotlin for even less boilerplate and null handling.