Do I need to create new mockup templates to work with Bulk Mockup?

You can use any mockup template available in the market. It should have a smart object layer.

You can download templates from websites like creative market & envato elements.

You can even create your own mockup templates. Tutorials below

How to create mockup template compatible with bulk mockup

How to convert jpeg mockup to smart object based template (compatible with bulk mockup)