Beachtek DXA-GO Two-Channel Adapter/Bracket for GO Wireless Receiver and Camera

Yes you can use the TRS to TRS Cable included with the SmallRig Forevala W60 system to connect it to the stereo mic input on the Beachtek DXA-GO.

Yes it will work with the Rode Wireless GO II system

You have the option to ether come out to your camera in stereo or mono. To get each mic on its on track, set the output to "Dual Stereo." "Dual Mono" out mixes the two mic's together.

YES. Assuming that your spell-checker transposed "shot gun" to "shut in" mic. My DXA-GO (untested and unused so far) has a shoe-mount on its top surface for a stereo shot gun mic and a stereo input for such a mic. Additionally, on each of two sides there is a shoe mount to add a Rode Wireless Go mic, left and right. And there is a switch that lets you select for either mono or stereo output. Dual trim controls can independently adjust each channel. On the back side as shown in the picture, there are left and right mono inputs (from Rode Go receivers) plus a stereo input -- I would assume from either a shot gun mic or the combined input of either RODE GO Stereo or mono Receiver. I do not know whether or not there is a way to use this device for three separate inputs. Pictured as an out on the right next to the various inputs, is the stereo/mono output to the camera. As an amateur looking at my device, the first two answers to your question and having scanned the instructions. GOOD LUCK.

This is an attenuator devices, the knobs are for gain, not for volume. The knobs are smooth.

Yes, it can work with other wireless microphone receivers although the size and shape of the DXA-GO was designed specifically to accommodate the size and shape of the Rode Wireless Go receiver. The Sennheiser G3 receiver is larger than the Wireless Go receiver, but it could work, depending on your camera and the amount of space needed. For comparison, the Wireless Go receiver measures 1.7 x 1.8 x 0.7" while the G3 receiver is 2.5 x 3.2 x 0.9". We do have other 2-channel passive camera mixers with 3.5mm TRS inputs and outputs that will work in exactly the same way and just a different configuration than the DXA-GO. Take a look at the Saramonic SR-AX100 Passive 2-Channel Audio Adapter for DSLR Cameras (B&H # SASRAX100) and Kopul CMX-1-V2 Two-Channel Mini Mixer with Shoe Bracket (B&H # KOCMX1V2) which are both compatible for use with two wireless receivers like the Wireless Go or G3.