Both the jBPM Console NG and the Drools WB projects are entirely based on Uberfire (Errai + GWT) so you can look at both to find out best practices about how to implement or extend the functionality provided in KIE - Workbench. Take a look at the jbpm console ng repository: https://github.com/droolsjbpm/jbpm-console-ng/
You will see there that we have different components inside a single project, and each of those components can be integrated into different distributions. The jBPM Console NG Showcase is just one distribution of all the components that are inside that repo plus some extra components that are required.
Notice that each component (project inside the repository) has three sub projects called: -api, -backend and -client. I strongly recommend you to follow that approach
If you are going to create new components. The Dashboard, Form Modeller and Process designer are embedded components that at some point we hope to get migrated to the same technology stack as the rest of the infrastructure.
I suggest you to read this article if you are interested in how all the pieces fit together and keep on eye on the blogs because I will be posting an example about how to create new screens and components soon.