Yes, according to Dell support, the webcam works with Mac OS.

According to the Dell manufacturer's website, there are no USB-C ports on the monitor. Connection via USB-C with the laptop is therefore also not possible. The connection to the built-in USB hub is via USB-B and 4x USB-A + 1x 3.5mm AUX connections are available: https://www.dell.com/de-de/shop/dell-6858-cm-27-inch-videokonferenzmonitor-c2723h/apd/210-bdsm/monitore-und-monitorzubeh%C3%B6r#techspecs_section