You can already use web components in Aurelia 1. There are no differences (that you need to worry about, at least) in v2 regarding using web components.
How do you expect to use your Stencil components? Are they already built and you only put the result web components into Aurelia template (simple)? Or are you looking to integrate more tightly with Stencil (i.e. write Stencil code in your Aurelia project and build them together)? Or mix Stencil components and Aurelia components (urgh… what?)?