Put it in Tow haul and let it do its thing.
Or don’t worry about it on the uphills as it will downshift as needed. Lock in a top gear you want if it’s hunting (not likely on a new rig).
Downhill, you can manually downshift it a cog or 2 to use engine braking if you don’t want to let tow haul do its thing.
You’re not gonna hurt anything by keeping the rpm’s up but you’ll use more brakes going down if it’s coasting in top gear at low rpm’s and you’ll have less power going up if it doesn’t downshift.
But it will do both for you about as intuitively as the average driver would do it.
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold