The Draytek Vigor 120 is optimized to work as a modem with the Apple AirPorts, so that would be the simplest and best route to take.
Whether or not the DrayTek Vigor 2710n could possibly be configured to operate just like the 120 is a questions for your Internet Service Provider and/or Draytek support.
Start with your provider first to see if what you ask is even possible....and if it is.....whether they will help you with this and support this in the event of problems.
If your Internet Service Provider cannot answer, you might try Draytek support, but keep in mind that your ISP may not support you if you make any changes on the 2710n and have any future issues.