Hello there @Rhubarb!
Thanks for reaching out to the Community! Sorry to hear that selecting a rack has proven to be a bit confusing.
If you are looking to go with Aeroblade system, you will need three components. You will need the Thule Podium Fit Kit in size 4047, a size large Aeroblade roof bar and a size medium. This will complete your base rack system.
As far as the Thule SUP Taxi XT, it is designed to fit all Thule rack systems!
With those items, you should be good to go!