Kieth,
Also, do not update your new GT2's FC in Betaflight or the ESC's in BLHeli. Unless something has changed, you want to stay on BF version 3.0.1. I've seen a few guys totally screw up their GT2's trying to go beyond 3.0.1 and updating their ESC's to try to run DShot. Again, unless something has changed, the ESC's are not compatible with DShot.
The first thing I do when I get a new bird set-up properly is use a screen recorder to make a video of all my settings in BetaFlight. I then do a CLI dump and copy/paste the data into a text file. I also go into BLHeli and verify that all of my ESC's are showing up with the same version of firmware on them. Short of doing that, you should be able to just fly the dang thing without messing with too many settings.
Jerry