Are you going to spend any time at BBNP? Great time of year for it.
Marfa, Ft. Davis, Presidio, Alpine and Terlingua are all worth checking out, if you are settled on Big Bend country. Davis Mountains State Park and Ft. Davis National Monument are both amazing. The Davis Mountain loop drive is spectacular, and takes you by the University of Texas's McDonald observatory.
https://mcdonaldobservatory.org/
I could go on and on about this region, so I'll shut up now lol...