I live in western Louisiana about 20 miles from the Texas state line, so know the area fairly well, but am limited on ability to make specific RV park recommendations. A lot depends on what you like to do.
The eastern part of Texas ranging from Texarkana to the north side of Houston is generally considered to be the piney woods region, there are no major cities in this region, it is filled with piney woods as the name implies, but also has a number of popular bass fishing lakes and small hills. many small towns, some fairly good food, but nothing really that is easy to pinpoint when it comes to attractions.
Moving west you get into the Texas Praries and Lakes region, the piney woods give way to grasslands with slow rolling hills, the northern end of this region includes the DFW metroplex, the southern end includes that area between Houston, and Austin / San Antonio with a number of quaint interesting little towns, look up the towns of Shiner, La Grange, Round Top, Brenham, Washington on the Brazos historic site, etc.
Moving west from there you get into the Texas Hill Country which starts on the west side of Austin and is a region about 100 miles wide and maybe 300 miles north to south (remember everything is bigger in Texas) This is the area where things start drying out as you move west, in the Prairies and Lakes region you might see the odd cactus, but mostly it is grasslands, when you get to the hill country the vegetation away from running water becomes much more scrub brush with some cactus and lots more exposed surface rock, though still generally covered with vegetation. The cities of Kerrville, Fredericksburg. Bandera, Llano, Lampasas, etc are all in the Hill Country. In recent years a number of wineries have popped up in this region, it is also a popular weekend getaway area for residents of Austin, San Antonio, and even the DFW metroplex. With natural outdoor activities, rivers known to tubing float trips, hiking, quaint towns, good food, etc. Moving west from here you get into Big Bend country, towns get few and far between things get much drier, and there is a variety terrain much of it consisting of high desert. Places of note are of course Big Bend NP, as well as Marfa, Fort Davis, Pecos, etc
This still leaves the coastal region, the south Texas plains including the Rio Grande Valley, as well as the Panhandle, though why one would want to spend much time in the Panhandle any time of year is beyond me.