1.Once approved, they will discuss with you the options for delivery based on your circumstances. But no, you will not get it while you are standing at the counter in the office. Depending on several factors, but mostly on the time of your appointment, you can usually pick it up in a few hours - so try to get as early an appointment as possible. If your appt is late in their day you might have to pick it up the next morning.
2. Yes, supporting materials should/will be returned at the same time as the new passport.

Ensure you have all needed documentation and photos. More info here: Apply at the Houston Passport Agency (state.gov)