Do I have to use PEPPRO with looper?

No. PEPPRO by itself does not specify any cluster resources, so you could just roll your own and submit individual jobs to a cluster however you choose. But because PEPPRO is already looper-compatible, the easier way is to use looper's built-in template system, which looper uses to build flexible shell scripts for job submission. These templates can be used to run jobs in a container, to submit to a cluster resource manager, or both.

Will PEPPRO run on a mac?

The pipeline has been successfully run in both a Linux and MacOS environment.