I installed the kit myself. On the rear of our cars, the camber arm is not adjustable and toe adjustment is limited. I took my car to an alignment shop before installing the camber,toe kit to get a baseline readings. I did this at standard and low suspension settings. I suggest you do the same--no adjustments just take the readings. After you install coilovers, you back to the alignment shop and see if the install changed anything. While this sounds like a lot of effort and expense, getting readings only from an alignment shop was not expensive. After install of your coilovers, if rear camber is outside of -050 to -0.70 (this spec comes from N2itive). them I strongly suggest adjustable camber and toe arms. The issues with the Tesla spec is that the range for camber is way too large and results more than likely in excess inner tire wear. After install of your coilovers and adjustable arms, have you car aligned at the riding height you will use.
I followed all In2itive's instruction and specs for the alignment. My car is great. Don at N2itive was a always available to answer questions I had along the way. I am surprised to see your comment that they are out of stock. I did wait a long time for my kit, but understood that they had good supplies on hand. I would call or email Don and ask directly.