I have the Topeak Uni Super Tourist rear rack with the the quick-track system for Topeak MTX rack bags. You can just slide the rack bag on/off and there is an one button push to release the bag. The Topeak MTX quick track bags come with a handle and a shoulder strap for easy carry. There is also a spot to attach a rear light and water bottle holder on the back. I have the 22.6L MTX DXP trunk-bag and 16.6L MTX EXP trunk bag. The side panniers are the same volume on both; but, the top on the 22.6L trunk-bag has an extra zipper to expand the volume capacity up if you need a touch more space for items. Other than that, they look identical when in the smallest configuration. Just make sure and go for the quicktrack bag and not the bag with only velcro straps.
I also have an med/large Osprey Radial 34 daypack. It has a rigid back panel to help with air flow to cool your back, tons of storage compartments and space, built in Hi-Vis rain cover, and very comfortable to wear for hours.
I scout sierratradingpost.com often. I managed to hit some panniers that listed for $90 each for under $25 each. Worth checking from time to time. Google can be set up to make daily searches as well. I also found Connex chains, great lubricants, some hardware and lights all on very low closeout prices. I never mind the last years model unless the current upgrade corrected some horrible problem. Easy to sort with Google.