You are doing the right thing. Using User ID (email) instead of the weird people field type is what I was doing as well. Many do the same.
Of course you can filter any list by an email in Power Apps. Filtering my email is not different from filtering by any other string-based field. Sample steps:
- Add Office 365 Users connector.
- Get current user’s email like so
- Now you can filter your SharePoint lists by email:
Filter('My SharePoint list', 'Email'= Office365Users.MyProfile().Mail)