I'm hoping it will be okay for a one night S Rim trip....
Almost anything is okay for a one-night trip almost anywhere.
For my 10-day backpack in Yosemite, I took a
GoLite Odyssey and was impressed at how it held up, comfortably held 21-30 pounds (depending on how much food and water I was carrying), and how easy it was to pack and unpack. With my sleeping bag in the bottom and sleeping pad lashed to it, it would actually stand up, making it very easy to load and unload. It swallowed my
ballast bear cannister, even on its side, and held all my gear without even using the extension collar.
On shorter treks, including my last two-nighter in Big Bend, I took a smaller, lighter (now discontinued) GoLite model. It didn't comfortably carry all the water I needed but was fine after the first day.
The tendency, even for 1-night trips, is to over-pack. Don't skimp on insulating clothing (and dry clothing for camp), but put everything else in a harsh light. Just because you have space in your pack doesn't mean you have to fill it.