Performance of local template vs shared template vs regular screen

From what I already know from browsing the forums, using shared templates can potentially slow down a project. My question is whether using a regular local template will cause any loss of performance to my project.

What is better for performance? Creating a main window and copying my graphics multiple times or creating a local template, and using 3 instances of said template in a main window. The project I am working on is not very fast as is, so I would like to know if making local templates will degrade the performance or not.