I've been using Mobile Entry (the app) and in the past I seemed to have been able to enter the U.S. quicker than people on Global Entry. In recent times however, they haven't had a dedicated line or really adhered to how Mobile Entry should work at the airports I've flown into (LAX, JFK)
I've found the best approach is to use the Global Entry app and if there is no specific signage for Global Entry app users then I start telling the staff in the immigration hall that I use GE app and I generally get pointed straight to a short or non-existent queue for an agent.