I'm on a stock, unmodified 6.0 Nexus 5.
Just a couple of suggestions. The spot to tap to open the checkbox "allow when device in use" is difficult to find. I almost have to tap between the entries to make it show. Not sure if this is a bug or feature. Also, the ability to filter by user or system app and bulk enable or disable for wifi or mobile would be fantastic, maybe a paid upgrade feature?
Overall I love the app. Thanks for thinking of the non-root community!