I've successfully created a new People display template (Item_Person.html) and associated result type, and used it on the peopleresults.aspx page. Now, I'm trying to achieve the same effect on the results.aspx page. According to @matthew-mcdermott in this postthis post, it is using the Item_Person_CompactHorizontal.html display template so I've copied that template and created a corresponding result type. However, I cannot get the custom display template to be used on the results.aspx page. If I explicitly choose that template, it will show my changes but it does not when I select the template based on the result type.
Moreover, I cannot seem to locate an existing search service result type that utilizes the Item_Person_CompactHorizontal template, so perhaps this customization is not possible without editing the original template?
I've also documented my issue here, with screen shots.