Austin for street, arch., music, football, and food.
Gruene, then San Antonio for street +architecture
Lost Maples state park for foliage colors.
Then back towards Houston along 90A or the parallel rds to the north side of I10. German and Czech.
Check out Texas Highways magazine archive for "spots" and photos.
There is the Missions trail across the same general coastal area. Search for Texas historical driving tours of landmarks.
Good time of year to visit !
Plenty of fall festivals then.