how to create a dynamic group of all power users?

I am also seeking out a way to group Powerusers of a similar profile, and Superadmins would love community response to see how others have done that. 

As for People managers who can see the “My Team” feature, we have that information coming from our HR system, Workday, that populates someone's Docebo user profile, we have a user field “People Manager = 1 or 0” and we've created a dynamic group with that. We have Workday Docebo Connect in place to bring that user information in to populate user profiles and support our Docebo branch structure. 

@YFDK I usually use one of the user additional fields for this purpose. IN one case, we use the word “admin” in one of the custom text fields and then create a group from that attribute. All you need is a way to get that text input as part of your onboarding or admin profile creation (depends on whether you have users use their personal profiles as PU’s or whether you create manual PU accounts; we use the latter in favour of keeping the users personal leaning journey separate from their admin tasks and permissions...better for security and compliance as well.

We have power users complete some specific courses on Docebo University.  We have a course set-up in our instance where folks upload the completion certificate from that.  Completion of that course is used as the filter in a group.