I am not with Laminar Research; just a flight simmer from downunder.
Like you I started with XP10 and now ventured to XP11. My system is currently mothballed as well.
The disc version of XP11 also requires disc 1 to be installed in a disc drive. Unfortunately XP11 does not have a USB dongle that substitutes for disc 1. I have raised the issue with Laminar and their advice is this is not on their "to do" list.
The design and configuration of computers are changing very quickly. If you purchase a new PC these days they are generally supplied without a DVD drive. To have one installed would be an option predominantly for a purpose built machine.
So, the bottom line option is to purchase a digital download. Depending on the supplier of the DVD disc set the only advantage you will get are a few extra discs with additional aircraft. because I have no interest in these aircraft I have not installed them
Provided you purchase the official and original digital download from Laminar Research ie not the 3rd party Steam hybrid, you will have your copy of virtually immediately (depending on download speed). I would suggest you setup a backup copy of the software in a safe place along with product password key details. I understand you will receive an email message regarding your purchase. This message should include your password key.
I also understand you have to be connected to the internet at all times when running the digital download as the software performs a "silent" check on the validity of your software at various times and you are not running two versions at the same time. Others have reported in this forum that they have to re-enter their password key on the odd occasion so it is important to have that number located in an easy access location.
Where to buy? Go to the Laminar Research (X-Plane) website at https://www.x-plane.com/ Click on "Buy it" and follow the instructions.
Good luck and welcome to X-Plane 11 world.