I have created custom sub-templates for several of my K2 categories. Is it possible to set a different default display mode for each of the templates. It seems logical to insert an override within the template itself in order to achieve this. For example, K2 Category One will display the gallery in artistic view if I select custom item view sub-template one. If I apply custom item view template two to K2 Category One, the gallery would be display in the sleek view.

ML

Yes you can. Check the documentation please:

If we wanted to override the popup engine and the gallery layout as well, we could use something like:
{gallery}folder/some_folder:200:80:1:2:jquery_colorbox:Galleria{/gallery}