I am a HGVC, a Wyndham and a Holiday Inn Club Vacation(HICV) member. So I know what HGVC is like and what these TX choices compare to that.
Very few Wyndham San Antonio La Cascada resort show up in RCI weeks inventory, I haven't checked Points inventory much since I own Wyndham points that is usually my avenue, but I have been known to pick up good deals on the week side of RCI. What I have seen is off season 1 BRs at best. This whole resort is Wyndham Points only owners. No fixed weeks at all.
Riverside Suites has a longer more convoluted history, even before Wyndham got in the game there. I believe it is dual II and RCI. I think II gets more of the units that are not participating in the Wyndham points, I do believe Wyndham points participation is not the majority of this resort. I think there are a majority of fixed week owners.
Both of these are downtown San Antonio.
There are several Worldmarks by Wyndham that are more countryside, but the New Braunfels location is close to Gruene, New Braunfels and San Antonio and makes a great base. Holiday Inn Hill Country (formally silverleaf) is also countryside but is also a great base.
Since I live in TX, I have stayed at all of the Wyndham's and Worldmarks, and most of the Holiday Inns timeshares in Texas.
I would stay at any of the Wyndhams or Worldmark's if you could pick them up. All do have good bases for area trips. The most isolated in the Hunt location called WM Spicewood Springs. Nice units, nice views, but in the middle of nowhere but close enough the West End of the Texas Wine Trail to make it worthwhile. You might get lucky and see a few of these Wynd or WM in RCI from time to time, but on OGS might be more useful for these locations.
Holiday Inns that were formally Silverleafs are great if you can get a presidential 2 BR 6/6 configuration or a 3 BR Ambassador 10/10 configuration. I would avoid lodge units 2 BR 6/4 configurations. There are a LOTof HICV (former Silverleaf locations) to be had in the weeks inventory. The other NON former silverleaf HICV in Galveston is a more consistent choice and any unit would be great there, but it only has inventory in the points side of RCI.
I just did an RCI week booking at the WM Marble Falls location and it was a great base. There are a lot of things to do all within an hour of that location.
PM me if you want some specifics.