2.54mm Dupont 20-Pin (2x10 ) Right Angle Motherboard Header Connector

No, USB 3.0 headers are 2.00mm in size. Where this is 2.54 this is designed for Power/Rest Switches. USB 3.0 does not use the dupont system. They use a system called MilGrid. The Connectors/headers are much smaller. Check Molex website they make a bunch of different headers that will work for USB 3.0 headers.

In theory it should work, however without personal experience trying that, I can't say for sure.

It would not work, USB 3.0 headers are 2.00mm, This is 2.54mm. I suggest taking a look at Molex website at the MilGrid series, They have a few angled headers. This header is designed for the Power & Reset Switch.

If the 2 headers are right adjacent with no gap it shoudl work. Hard to say with no pic.