To answer the essence of your question before getting into some specifics, the difference between the cross bar and direct connect style of base plate can be broken down like this: the Roadmaster Direct Connect Base Plate # RM-523173-5 is going to provide for an easier connection to your tow bar than the Roadmaster Crossbar Style Base Plates # 523173-4 .
A lot of people stick with Crossbar style base plates because they have an old tow bar they want to continue using from a previously... view full answer...
If you have wheel liners then you want to use the 135 degree bend kit part # WM8001-135 but if you have wheel covers then you need the 90 degree bend kit part # WM8208 instead.
Attached are demonstration videos of each for you to reference. view full answer...
You are correct in that both the T-One Vehicle Wiring Harness part # 118755 (no longer available) and the T-Connector Vehicle Wiring Harness part # C56372 are a fit for your 2017 Chevrolet Sonic RS/LT Hatchback. There are few differences between them as they both plug in behind the tail lights without any cutting or splicing involved. They are essentially just two different manufacturers version of the same product. They both have the same purpose and will plug into the same connector on... view full answer...
The difference between the # RM-146-7 and # BX88206 coiled 7-wire to 6-wire cord is minor.
The Roadmaster cord can be expanded to 8-ft and the Blue Ox expands to 7-ft. view full answer...