Hi, maybe I can help...
This is the rotary from harbor-freight, which is supposedly the same as the vector.
Anyway, the connection between the backing plate and the rotary seems to be universal. The pads screw
on to the rotary [not
in like on the PC].
It comes with a 7" velcro backing plate, which seems to be fine to use, but I don't have any 7" pads.
I got the 5.5" pad from Top of the Line, and it seems to work good for me. I have 6" Buff & Shine pads and 6.5" Lake Country pads, both purchased from TOL.
In the picture, the pad which is partly yellow is the Velcro backing plate.
Beneath that is this heavy rubber pad....I'm not sure what it is for...maybe to tie the included wool bonnet over. I don't recommend it.
In that little bag in front of the polisher is the handle, an arbor wrench to keep the rotary from turning while installing the backing plates (which is unnecessary because the rotary actually has a lock button), and an extra pair of brushes.
I finally got up the nerve to use it on my car, and I guess I can say that I dont' know how it can be better. the "soft start" feature is kind of annoying if you're trying to feather the polisher along, but I've learned to live with it.
I did end up with light buffer swirls on my car, though.

I guess I gotta improve my technique or product selection.
Any more questions?