You will NOT get pulled over for ride height. Basically, your car's frame can't be lower than the bottom of your wheel. This makes 18" wheels better than stock rims for lowering the car (legally)
The guy who told you he got pulled over for 18" rims and drop is a moron. It was his exhaust that caught the cops attention. I'm sure the cop just mentioned the other mods in a negative way, and the guy took it wrong. You really are THAT worried about tickets, just go back to stock exhaust.