The back roads of Texas are in general better than the main non-Interstate roads of most other states.
For our first time, out of state visitors it might be of value to know the "official" levels of highways in Texas other than Interstate routes.
U.S. Highways: as indicated, better than in most states.
Texas State Highways: often as good as, or better than U.S. highways
FM or RM Roads: (Farm/Ranch to Market) not as wide and often much more curvy, yet I do not hesitate to tow my fifth-wheel on most of them.
County Roads: No recommended unless you know. A few are as good as FM Roads, but some would be completely unacceptable.