When I towed our 16K 5th wheel at a combined 24,500 I found that even with drum brakes that set the controller to Heavy Electric over Hydraulic worked better. Post 2013 or so RAM made a change to the controller. It lessens the brake output when one gets down to slower speeds(like under 20 or so). Many have complained about this. Braking is controlled by pulse width modulation to the trailer. People had graphs of the signal output to the trailer.
Hopefully RAM has fixed this, as I no longer see many post about it.
Mine is a 2015 3500 SRW 4x4 CTD.
I had a MAX Brake controller in my 2001.5 RAM for last 8 or 10 years that was the best made at the time. I let it go with the truck and should have kept it. Brakesmart was also a great control. Both are gone.
Chris