Congratulations, and good on you for being more future-focused than likely many of your peers. My son, at 31, has had a Tesla plan since 2008 when he started yakking my ear off. But that plan is waiting for Model
≡.
70D great choice, although all your friends will seriously rib you for not getting Ludicrous. It's something to do with the age, I think.
You'd better use the pre-delivery time to think up some really scathing comebacks!
21"? Don't really see what benefit you get (better traction, better looks) for the downside (easier curb rash, higher wear (more frequent replacement), higher road noise). I'd stick with 19's, but then, that's just me, I'm sure others find the 21's indispensable.
I find the air suspension great for getting into steep driveways and ferry-boarding.
The pano roof is just great. Closed, it cuts out nearly all the heat and the sunlight glare. Open, it's... open! Not quite convertible, but very very nice on good weather days.
One caution about insurance: you mentioned up-thread that you'd be "occasional" with your parents as "primary". But, if you're the one who really is primary, listing it the other way to save some annual $$$ could very quickly void the insurance. And that's something you definitely don't want.
And, I'll echo all the others here, no matter how much you can trust your friends, you cannot trust them to treat your 70D properly and safely. Stick to giving rides only.