Ventilation is air exchange.
Draft is a breeze hitting them.
If you are just north of Houston, it's not really an issue with you. I still would like to keep direct breezes off of them in the winter and mainly during the worst of the thunderstorms you will see, but you could get by with one entire side of your coop being wire. Just put their roost sort of back in that nook formed by the three solid walls.
For us mortals sometimes faced with actual cold weather, the way to handle the problem is placement. Have the ventilation openings higher than they are when they are on the roosts. The air will move above them and take away all that nasty stuff, which is lighter than air, by the way. You do need openings higher than the chickens to get rid of it.
Any real drafts will be over their heads.
Where you are your real enemy is the summer heat. A lot more chickens die from excessive heat than from cold. For you, a breeze hitting them in the summer is a good thing, not a problem.