Most (if not all) Vaadin enterprise grade applications are built in non-accessible private repositories of companies… so it’s pretty hard to get you an example.
Some good examples publicly available are from:
- @SimonMartinelli GitHub - 72services/jtaf4: JTAF - Java Track and Field
- @Tatu2 GitHub - TatuLund/bookstore-flow-ee: Java EE version of Bookstore Vaadin 24 multimodule project with EAR packaging
In the end most of your questions can be answered with “it depends” and “how you like it”. Even building views in the constructor vs. life circle is a big topic by its own. Probably the only easy answer I can give you: put your css in your theme and don’t (overuse) the getStyle()-API - this can quickly get really messy.