Need more help for first cross country trip.

If you are talking about US 70 in New Mexico it is good four lane with virtually no traffic all the way across the state. Depends on where you are going in New Mexico.

If you are going SW through New Mexico take I-40 to Amarillo, I-27 South to US 60 West, then pick up US 70 West in Clovis.

If you mean US70 you would need to get on I-40 at times going through the mountains in Tennessee.
I would take I-90, I-84, I-81, I-40, at Nashville take Rt 840 back to I-40 to Albuquerque. The cities you will go through are not that bad. Try to time all cities not at rush hour. We go through about 10am. Once you get the route, we can help with stops.

I-70 is an interstate highway and is definitely not a two lane road. Unless you mean two lanes each way which it is in places.
Parts of most interstates are concrete, depending on who the states favorite contractor is. You may have seen online a Rt.70 that is a state highway somewhere but the interstates are good to make time on, I-70 included.