The Tesla app payment was instantaneous. I had already transferred the funds to my checking account. The Tesla app uses the Plaid interface which is an API that banks use to talk to each other. Through the Tesla app I gave my bank, then the Bank of America UI showed up in the app and walked me through the normal logging in including their 2FA process. It knew I was doing a transaction with Tesla. I thought it was quite secure. Once it was completed the Tesla app showed I had paid.
Texting my area Tesla sales office was the only effective way to communicate with Tesla. Once the VIN was assigned their local delivery specialists were quite responsive to texts. Occasionally a text would come from corporate, but most of the time it was the local delivery folks.
Tesla will contact you once a VIN is assigned. A VIN assigned means that the vehicle is currently being manufactured, or just about to, or just finished. Tesla will likely text you to tell you VIN has been assigned, plus it will show up in the app. Then your car has to be transported to the delivery center. Cross country it travels via the “Tesla Train”. Enclosed car carrier cars three levels packed with Teslas. I found some videos on YouTube.
In addition to the VIN there will be some invoice type papers (sales agreement) you need that will be provided via the app. I got the VIN while the car was in production and then the sales agreement/invoice which had the VIN a couple of days later when apparently the car had exited production.