If I'm not mistaken, the coil suspension is equivalent to the "high" setting with the air suspension. So if this is correct, you should be okay sans air.
Regarding AP, I suspect you will like/appreciate it more than you think, especially if you roadtrip to Dallas or Houston. Even if you don't take any road trips, AP is so useful on the highway and in bumper to bumper traffic and even at stop lights when you are behind someone so you don't have to constantly pay attention to start moving. You mentioned not encountering much traffic on a day to day basis, but I still think you can't fully appreciate how useful AP is on a 24-48 hour overnight test drive. I believe AP has literally added years to my life with regards to the reduced stress. You will use it much more than you think and will probably drive more than you ever have in the past. I am constantly finding reasons to drive my car, run errands for my wife, etc.
You really can't go wrong. The sooner you get into a Tesla, the sooner you can be driving the future, good luck!
Alright, I'm gonna add it then
On the coil suspension, the default height is equivalent to the 'standard' on the SAS. Now I haven't tried the coil one on my driveway. Maybe I should ask the OA to swing by sometime.