I actually disagree a lot what people are saying about Texas and these apparent shifts to the Democrats everyone is talking about in this Thread.
You might considering something:
Texas Democrats had extraordinary lucky circumstances in 2018. Not only was Trump toxic in the Suburbs and that's why Lizzie Fletcher and Colin Allred won their respective Races BUT Texas also probably had the least popular Senator of the entire Country, Ted Cruz, on the Ballot. Combine those two factors and you get the Results that you actually got.
Also, Governor Abbott managed to beat Democrat Lupe Valdez 55,8 % to 42,5 % (13.8 Percentage Points) on the same Night so it was much more about a combined angry Voters upset at Trump & Cruz than Texas shifting.
You put a Generic Republican like Romney, Haley, Rubio, etc. on the Texas Ballot and they would win it by double digits like it happened in 2012.
Texas is still a Lean R State IMO.
Which isn't good for the GOP.