I40 thru flag staff has high mountains, but the grades weren’t bad. if you take i40, heck out the Road Kill Cafe in siglman azI-40 is smoother thru NM and AZ. than I-10 IMHO. AZ is the mountainous area (continental and Arizona divides are good climbs). Lastly, Flagstaff area is only area that's has snow possible currently.
Good luck and stay safe
We are traveling from Austin to Palo Alto California. I wanted to avoid as many high mountains as I can. Don’t know if we will be traveling on I-40 or I-10. Can anyone suggest a good route to avoid the least high mountains. Thanks for your help.