You are correct, there are two options for a Stealth Hitch on your 2021 Audi Q3. The Stealth Hitches Hidden Rack Receiver # 391AUDQ319 and the Stealth Hitches Hidden Trailer Hitch Receiver w/ Towing Kit # 391AUDQ319T.
Essentially the difference is that the Stealth Hitches Hidden Rack Receiver # 391AUDQ319 is only rated for use with hitch mounted accessories such as bike racks and cargo carriers. If you wanted to tow a trailer or anything else you would have to add the Towing Kit w/ Ball... view full answer...
We have not had a chance to install the Draw-Tite # 75218 on a 2015 Audi Q3 yet so I do not have the exact ground clearance measurements, but based on the two manufacturer provided installed photos I believe you are correct that it will give more ground clearance than the Curt # C13238.
If you are planning on towing with your Q3 you will also need a vehicle wiring harness # 119250KIT, and a hitch ball, ball mount, and hitch pin and clip which can all be found in the etrailer Ball Mount... view full answer...
I can understand why this is confusing! The Stealth hitches like the # 391AUDQ319 are a bit of a different animal than a conventional hitch, and the receiver that it comes with is designed only for carrying hitch mounted accessories like a bike rack. If you're going to want to tow with your 2020 Audi Q3, you'll instead want to use the # 391AUDQ319T which has a specially designed ball mount and 2" hitch ball that is designed for towing with the Stealth hitch. If you look at the notes for... view full answer...