Anyone registered to vote can choose a Republican or Democratic ballot. Many of the people on the Democratic ballot (in my area) are running unopposed, so it was a good opportunity to try to get the least crazy people on the November ballot. Also, the republican ballot has 13 propositions that are not on the Democratic one, so that’s your only chance to have a say in those (and IMO they are really really bad!)
I spent a couple of hours researching and all I got out of it was feeling like I needed to take a shower. Finally, I looked up the true Texas project, printed off their recommendations, and voted opposite those.