You certainly don't have to worry about any climbs or descents with your motorhome!
I'd advise you to get the 'Mountain Directory for Truckers and RVers'. We used it all the time not only for new routes but to refresh ourselves on routes taken in the past.
That said - from the Directory:
AZ on 93: From Wikieup, MP123, south to MP160 there are some 5-6% grades both uphill and downhill. (Keep in mind that even on interstates you'll find some 7% grades so 5-6% aren't biggies). From MP161 to MP172 is a long descent for northbound traffic & a grade of 3-4%. On descents, get into lower gear and let your engine brake do the braking.
On 93 between Kingman, AZ and Boulder Dam - ups and downs from 2% - 6%
Nevada: On 95 south of Goldfield, the northbound descent starts with 1/2 mi of 5% grade, then 1/2 mi of 1-2% grade then 4% for 3/4 mi into Goldfield.
Tonopaugh, NV has a very nice 'RVers-only' rest area for an overnight called Miller's Rest Area. https://www.campendium.com/millers-rest-area
Oregon: Hwy 20: west of Juntura, OR - Drinkwater Pass, EL 4212':
The descent westbound is 6% for 3 mi into Buchanan.
That's it! A very easy drive.