I never used a Toppeak rack.
I have a couple AddIt racks, very happy with them. Well made. Addit is rated for 30 kg which is over 60 pounds so they are built to be solid.
I picked up a hard sided bag that attaches to the Racktime racks at a swap meet, it was really cheap. But I have never found a reason to use it. But it appears to attach and detach quite easily, but I never tried it in adverse conditions.
For a while there were no RackTime dealers in USA, it will be nice if the brand comes back. A few years ago REI sold a couple of their racks.
I know that you can't see the AddIt rack in the photo, but I included anyway because it shows that the rack will carry a load. I use the AddIt rack on that bike for touring.
And, yes it was chilly that day. Thus the long pants, rain jacket, rain cover on helmet.