Just to be a completist, there are five districts that include parts of Austin. The Democrats hold one of them (Lloyd Doggett.)
In addition to M.J (Mary Jennings) Hegar and Joseph Kopser in the open 21 district held by retiring Lamer Smith, there is the 10th district where Mike Siegal is challenging Michael McCaul and the 25th district where Julie Oliver is challenging Roger Williams. In both of these districts in 2016, the Republican won by just under 60-40%.
With all this in mind, definitely think that Hegar is the strongest dem candidate in central TX, but maybe not in the easiest R district