You will see mountains towering above you, but you will mostly be on flat or slightly sloping roads. Don’t forget, giant semis with full loads will be traveling at 70 mph. If they can travel safely, surely you can.
Your daily driving on two lane roads in Nebraska is MUCH scarier and much much more dangerous than driving an interstate through the mountains! Think about it! On the interstate, you have wide lanes to travel along, with shoulders, sometimes WIDE shoulders, on either side of the road. On Nebraska’s two lane roads, the lanes are narrower and you are just inches from a head on accident into oncoming traffic. I’ll take the interstate any day!
Another thing about interstates in the mountains. Much of the mountains are bulldozed flat. Most of the valleys have been filled in or crossed with bridges. The landscape has been drastically modified to create the flattest roadway possible. There IS NO mountain driving on the interstates; there are only Mountain Views!
You will of course gain and lose elevation, but the slopes will be gradual over longer distances. You’ll have to give it more gas as you’re gaining altitude and at times will need little or no gas while descending. You can always use a little brake or switch to one gear lower if you want to slow down. But, much of your driving will be on fairly level roadway.
Slow down if you feel uncomfortable at any time. Maybe pull behind a slower semi and follow it for a while. Just be aware that they can slow down a lot going up hills.
Enjoy the views but keep your eyes on the road, and take it easy at some of the scenic rest areas along the way.