Which bike do you have? There may be different versions of at least the Topeak Tourist. I know the one I got was specifically for fat tire bikes with disk brakes. I don't think you want that one if you don't have fat tires. Looking back, I see you have the Rad Rover ST, so be sure you get something for fat tire bikes.
I've never used panniers, but I don't mind having that option. I don't see a lot of downside to having the option and not using it. Maybe sometime I'll want to do some cross country touring and need panniers. Even for a 40+ mile day trip, they could be used for a spare battery, water, lunch, etc.
Plus, I really like the ability to snap on different Topeak bags, should the need arise. It's basically push button easy to swap bags, or take one off to carry with you when you lock up your bike. There are ways to do that with other racks, but not nearly as easily.
I don't understand Rad's inability to keep things in stock. It seems to be their business model, but I can't imagine the number of sales they must lose because almost everything is just about always "temporarily out of stock." Of course I haven't used their rack, but, for me anyway, it doesn't seem worth waiting for when I know there's another excellent option available.
TT