That software will definitely allow you to try out FSD. I found that even on the aggressive setting FSD is still very conservative with unprotected left turns. Thankfully you will be able to give it a try for 3 months for "free".
As for refusing updates, I don't really think that is something to be worried about. My car has been connected to WiFi since the day I got it and I have the software updates set to advanced and nothing has come through yet.
So, enjoy your car when it arrives and hold on for dear life with your FSD trial.