I have literally never met a zerg that will continue with broodlords once you kill them all, because most like to get this 10-15 broodlord swell, thats pretty easy to kill if you are careful. I literally always drop 3 addition starports (making 4, 1 with a reactor). So I can quickly counter it if they try again. Also consider expanding aggressively and build redundant orbitals for scans and mules, will make scouting their base easy.
Mix wise, save your thors, and add marines (if you are infact going pure mech). But thats stylistic, any combo will do, and vikings will effectively only cut the number of tanks you can make at once, thats it.