Not only does Capt. R.H. Williams' name appear in books, he himself wrote a book in his later years called "With the Border Ruffians." Some of the names in the book he disguises (Gen. Bee becomes Gen. Wasp, etc.) and some are fully recognizable. He mentions the Nueces Massacre in his book with considerable sympathy toward the German Texans who were ambushed.
Capt. Williams was active in the CSA. TX State library archives show that he had the command of the mounted volunteers of Frio County, 3rd Frontier Division of the Texas State Troops. The only record I have shows 1863. Another source says the unit "never fully organized," so I suspect this Frio County duty was a sort of sideline for him. Capt. R.H. Williams served at one time under the cruel Capt. Duff and, regrettably, is reported by some sources to have participated in the Spring Creek massacre near Harper TX.
The book is in paperback and is entertainingly written.
As for Jake Vinton, he lived and ranched out near Frio Town near the Hilers, Blackallers, Slaughters, Woodwards, Louis Oge, and a few others. I'm rather certain that he's mentioned in the publication "Frontier Times." There's an online index to that publication, but I think you'll have to visit a library or the Frontier Times Museum in Bandera to read the actual text of the old magazines.