Both together

A page without a template of its own gets the closest template or code default. Two rules settle ties:

A template wins over a code default that is just as close. Editors can take over a type by making a template for it, with no change to the code.
A template made for no types comes last, after every code default. It is the layout for whatever nothing else covers.

IPage ◄── IArticle ◄── INews        code:       RenderRazorView<IArticle>()      for IArticle
                                    templates:  "news"                           for INews
                                                "fallback"                       for no type

an INews     → template "news"        the closest
an IArticle  → RenderRazorView        the only one for IArticle itself
an IProduct  → template "fallback"    nothing closer; a template for no type is last
                                      (with RenderRazorView<IPage>("Default") added: "Default")