in what way is it configured to match the DAC it's attached to
Some DACs "like" upsampling, and some others don't. The server is fully configurable to allow for as much upsampling as you (and your DAC) like, from nothing all the way to DXD/DSD512!
As Mike said, there are also a myriad of filter options, which alter the tonal balance slightly, allowing further fine tuning.
It also has a full Roon server inside, so you don't need that configured elsewhere. All you need is a NAS configured with file sharing. Point the SGM's Roon install to your NAS, and that's all!
As for the Aurender, I haven't compared it against the W20, but we did compare against our humble N100H ($2600) unit, and the SGM was in a whole different (superior!) league.