I travel to MT and back to SC every summer, so I cover a lot of varied terrain. I believe that my TV (Tacoma) could handle my 17 Casita
w/o electric brakes, but added electric brakes as a safety measure. In all my travels I only encountered one downgrade that was really long and steep, coming off the top of the Big Horns headed to Big Horn Canyon NRA. Here I had to be extra careful.
I am guessing that the real value of electric brakes is an unanticipated deacceleration while traveling on Interstate. Here are some common sense practices that are as or more important than the brakes themselves.
1. I keep my speed reasonable and use defensive driving techniques.
2. Allow lots of space between vehicles I am following.
3. Take lots of time coming off passes.
4. Have TV brakes checked before I leave.
5. Have electric brakes checked and adjusted before I leave.
6. My wife and I use a check list before departing each campsite no matter how routine it gets which includes checking electric brakes.
7. Make sure TV tires
have lots of tread, are sized correctly and are properly inflated.
I am sure you will do well. Enjoy MT and be safe!