That S2722QC USB-C port only delivers 65W back to the Laptop. That will not suffice for full operating capabilities. So you will have to also connect the provided 90W or 130W AC adapter to the Laptop. The XPS 15 9520 left side TB4/USB-C and right side USB-C/DP ports should deliver audio into the S2722QC speakers Line-out port. In the operating system Sound settings, you will choose the S2722QC as the Output device.
I just got an XPS 15 and I'm thinking of getting the Dell 27" 4K UHD USB-C S2722QC. If I get it I'll be using the USB-C connection. I have a couple of questions for those who have this S2722QC. Thanks, Mike
S2722QC, XPS 15, questions