I was looking into getting one of the selle smp saddles. I have one seat wedge from Topeka that has the quick release. Will the quick release part mount onto the selle smp saddles?

I have one of those Topeak bags and it worked from my stock saddle to my Brooks B-17. If you look at the Selle SMP you can see it has long rails for the quick release to mount to. I had to scoot my stock saddle back a hair to get clearance and my Brooks accepted the quick release with no problems. Looking at the length of the rails it should fit, the width of the rails is somewhat standard. When I had the bag mounted to my Specialized the rails flared out a bit at the back but the quick release still fit. Based on my experience with one bag and 3 saddles I think you'll be ok.

The standard clip for the Topeak seat wedge only "just" fits at the back of the SMP rails because of how it flairs towards the back. It will fit and I have one on my Klein with Dura Ace Seat post. However it works better with the Topeak extended mount. The flat stock one tends to work its way loose while the extended one has a better clamping arm. Just as long as you mount the stock mount close to the bend at teh back of the rails you will be fine. For me the SMP is one of the most comfortable saddles made. But my problems were never sit bone related but more of a Perineum issue.

The first priority is will the saddle work for your butt. Whether the seat bag clip works or not is way down the list. That said, I prefer seat bags that mount with straps as it's more secure and versatile.