While I appreciate the use of multiple PR templates, they are not as easy to use as multiple issue templates. This repo is a simple solution to a smoother workflow for using multiple PR templates.
The best way that I have found to make multiple PR templates usable is to create a master one that instructs PR-creators how to leverage the other templates that you have lying around. You can see what I have done by looking in the .github directory. Test it out by creating a PR against this repo!