I guess you mean Activiti Community Edition v6 and AngularJS v1.x. You have various options for your project and it's a question of what's best for you. You could write the UI yourself as an Angular app and call the Activiti REST APIs as needed. Or you could look at the kickstart app that comes with v6 and see whether the forms feature suits your needs. Another possibility is to use the codebase of the kickstart app as a starting-point and customise parts it to fit your application. If you were interested in using Angular2 then you could consider building a UI using the Alfresco Application Development Framework but that's currently centred around the enterprise edition and it seems you're more interested in Community. Alternatively the form stencil feature in enterprise (https://community.alfresco.com/community/bpm/blog/2016/08/31/form-stencils-101 ) could be of interest but it sounds like it your preference is for community.
If you go down the route of using the REST API then you don't have to work with the kickstart app at all. You can just run a spring boot app that contains the REST API dependency (see Getting started with Activiti and Spring Boot ). So then you're free to create whatever UI you please without worrying about forms. Alternatively you could create a spring boot app that exposes rest endpoints for each of the actions for which your UI needs to call the backend and implement those REST endpoints using the Activiti java API that you get access to with the spring boot starter.