Hungry Horse, MT to Theodore Roosevelt NP, ND

US2 is closer to the North Unit, I94 passes through the south unit.

US2 in western ND used to be notorious for oil field traffic, but with the downturn in oil prices and the pandemic that may be different.

Google Maps is suggesting a middle route MT200 (from Great Falls).

Some years ago I drove the reverse route. When I entered MT on 94 I debated taking 200 across, but with limited information on camping or motels along 200, I chose to stay on 94 to Miles City, and the next day took a diagonal route from Billings to Browning.

15/94 between Helena, Butte and Billings is somewhat mountainous (with broad passes), while 2/200 are quite flat and featureless - and fewer towns and services.

But decent roads (and speeds) all around.

I don't know what it's like now but in mid June U.S. 2 had a lot of construction. One stretch was several miles on dirt and gravel. lf I'm remembering correctly it was between Shelby and Havre.
Enjoy Teddy Roosevelt we sure did in 19.
It's been about 10 yrs since I drove 200 from Great Falls to Circle. Look at that road on Google maps and you'll see it's a long road with very few towns and those that are there are very small. Most of the time you don't even see houses, their back off the road out of sight. You'll see signs for such and such ranch and that's about it. It was a good road when I was over it but very narrow if any shoulder to pull off on

I drove that route 3 years ago. The speed limit on rt.2 outside of the towns was irrelevant as most were going around 80 mph or more.

US 2 to Wolf Point. Highway is good two plus lanes.
Once past Cut Bank, mostly down hill.