I have a Crux and went with a set of HED Ardennes from MyBikeShop for a second set of wheels. Good deal with the tubes, tires, cassettes, etc included in the price.

How much do you want to spend?
Tubed, Tubeless?
Brakes: 6 bolt or Center Lock (probably keep the same as what you currently have)
Other qualities?

Light, Strong, Inexpensive, Aero.

Choose 2.

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stick with same as stock setup, so tubed for sure. Not sure on the brake as it is a friends bike, but stay the same unless there is a compelling reason to switch.

Strong/Reliable would be goal #1. Light/Aero goal #2. Price would be willing to pay for quality, but to keep it reasonable. This won't be for racing or anything. But long life is a goal.