Since you're using Roon, please use Roon Remote app on Android. Alternatively, if you experience some issue with the Lumin Android app and you don't have an iPad yet, please try Linn Kazoo app or Bubble DS Next app.
L1 is meant to be fanless, zero-configuration and easier to use than NAS, although some people have reported a sound quality improvement compared to typical NAS. If you use a NAS, you'd need to install the freeware MinimServer. I believe doing Ethernet network isolation using fiber media converter (FMC such as TP-Link MC210CS) with LPS (for the Lumin-side unit) should also help with the sound quality.
Which input of Golden Gate 2 are you using? USB or AES?