I have only done the run on TX 21 from where it joins TX 71 west of Bastrop to where it crosses US 290 near Paige. It is a fine road, towed my 5th wheel on it.
I have found that state highways of Texas (as opposed to Farm to Market roads, which are generally OK, but more twisty-turny and more narrow) are very good, with perhaps a few exceptions, exceptions which I personally have not experienced yet.
one_strange_texan
Currently between RV's
Former 5th wheel owner (Montana 3402RL)