New bee ... to a truck this size. I tow with a 2008 Tacoma .
What setting should I use to tow with a 2018 f-250 diesel , like a two horse trailer with weight dist. hitch ?

I see tow/haul , I'm use to just drive(no Overdrive )

 

The 6.7 will have Select Shift, Tow Haul, and an Engine Exhaust Brake. Hill Assist etc.

So, basically a tool bag of towing, power/torque, shift and braking capability.

What you don’t want to happen is ‘shift hunting’ which is the OD kicking in and out, or continuous up/down shifts. Heat is a transmissions enemy. So, pulling a long steep grade and/or with steeper down grades, Tow Haul will help with shift limits and auto downshift points for braking (speed limited). Add in the Exhaust Brake with Tow Haul, and truck braking is almost nothing.
Select Shift, you can lock out up shifts, hold ranges M, and with the Exhaust Brake mod, can keep the truck in the best range/s for the current type pulling or grade environment.

I can decend our summit without ever touching the trucks brake pedal, with only Tow Haul and Exhaust Brake being controlled. Loaded, I may cancel out a top gear shift to help hold back an RPM spike or upshift, and just cruise.
Select Shift I use for the more ‘rolling hills’ and want to keep the truck near peak or moderate perf without it shifting or using Tow Haul, or Exhaust Brake..