Rvian seems to be contacting those who reserved a vehicle about 3 months before they expect to deliver a vehicle to you. I have heard about two owners who placed a reservation quickly, and they where contacted and the Rivian person said they could get delivery by the end of October, wanted to confirm they still wanted the vehicle.
They reported that making final decisions such as color, options, and then sticking with that decision would help avoid any additional delays.
For instance, say you pick blue car with black interior, and they put that vehicle on the schedule for you. If you should change the outside color, you might get pushed back to another delivery date. There might also be a problem, say 40,000 people order the kitchen option, and that company can only produce 300 a month. It might cause a delay. Yet I think if the helpful person from Rivian says "We will delay your order into 2022 if you want the kitchen option" most will say forget it. . .
How to drive a Rivian quickly? Apply at Rivian as a vehicle delivery consultant. Take a new Rivian to customers all across the country! It works for those of us who are retirees, and can take time to get a new job. Don't know how much it will pay, but heck, you get to drive a new Rivian off the trailer and into someones driveway!