A few questions that I’m unable to find answers for..
1. EMU software can run on one machine at a time, but you can deactivate on one device and reactivate on another quite easily - covered in this video: https://www.youtube.com/watch?v=ADg6wAHNvaY or you may buy another subscription.
2. Connecting to your visualizer will depend on what your chosen visualizer software requires - do you need an Art-net stream? If so, you can send Art-net from EMU to your visualizer software.
As example I know a few programs people use (sure there are more, I am just sharing which I know):
MagicQ (attached video, sorry for the poor quality), has free version which could be enough for you, which is good: All you have to do in MagicQ is built the exact same setup as in EMU. You then have to select the right IP address in EMU, that corresponds with the input IP in MagicQ. You can then run the „test“ setup in MagicQ from the input source. This will basically run your EMU show through the other software. And since that other software has the build in visualizer, you see everything you are doing in EMU. These two videos were the ones that may help a lot with 1) getting to know chamsys in the necessary depth (because you have to built the exact same setup) and 2) setting up the network connection.
Capture (I think it has only paid versions). https://www.youtube.com/watch?v=ENoRfXE_G10&t=745s
Under the video you may find useful link with another visualizers:
but I don't know anything about the another visualizers.