The Thule AeroBlade Edge Roof Rack system you referenced, consisting of parts # TH7602-TH7602 is a fit if you can find the discontinued fit kit 4002. Instead you can use Crossbars # TH711420, Feet # TH710601 and Fit Kit # TH186025. This is a correct fit for your 2007 Audi Q7 that has flush mounted rails that run front to back. This is a complete rack system.
However, as you note locks are not included but instead offered as an option. The lock kit is part # TH450400 and this includes... view full answer...
The Trailer Hub and Drum Assembly - 5.2K and 6K E-Z Lube Axles - 12" - 6 on 5-1/2 - Pre-Greased # AKHD-655-6-EZ-K you were looking at come as a quanitity of one hub. This hub includes the inner and outer bearings, inner and outer races, grease seal, grease cap, and lug nuts needed.
You will need two of the # AKHD-655-6-EZ-K per axle.
I included a few videos of the # AKHD-655-6-EZ-K for you to take a look at. view full answer...
The Draw-Tite # 75950 does not come with a wiring harness but there is one available for your 2014 Audi Q7.
For the harness you need part # 119250KIT to add a 4-way, which is going to allow you to power your trailer's lights. view full answer...