Either the .300WM then if you shoot it well...or if meat hunting then take a neck shot with the .270...just in front of shoulder.No tags. Elk are considered exotics in Texas. Open 365, no limits.
I have everything I listed. The .300WM my father bought to on his only elk hunt (Montana. He got skunked). So it's tempting for sentimental reasons.
Unfortunately I don't. There's not a lot of trees out there. Mostly scrub but supposedly some decent elevation changes. Regardless I wouldn't take anything over 300 yards.