Concerning the Light Group issues, it seems there’s problems if we update android yeelight app (install new version on top of a previous version)… so i advise you previously completely uninstall yeelight app and just then install the new yeelight app version from Google Store! It worked for me and now i can create and add devices to Light Groups!
About the issue of Light Group issue, we have found the root cause and fixed it. Thanks for your feedback.
That’s great to hear! Thanks 
It will be possible to implement schedules for Light Groups on new yeelight app versions?
android nougats notification works differently. turning off the notification kills the app from being running in background
I think that even when application doesn’t show notification - that removes (or can remove if RAM is needed) the app from the memory… so it really doesn’t matter. No notification, no matter HOW - you won’t have it running in the background…