Re: S16's ( dummies guide!)
The routing webinar went over the S16's - if you can set one up, setting a second up didn't look any more special - it's just another bank of inputs/outputs that shows up as a source to route from/to.
X32 Live! Webinar: Routing overview - YouTube
Around 13:00 they talk about the inputs, and around 14:00 the talk about two or more S16's and the AES50 ports. At 38:50 they start talking about output routing on the AES50 ports to the S16's - if you start watching there I'll bet that will help you. But don't get hung up on their being two or "daisy chaining" or other concepts - if the S16 is plugged in, the inputs/outputs should show up in the routing section for you to pick and choose.
At the risk of confusing you, you can have up to three S16's on each of the AES ports for a total of six active in the console at any one time - that's obviously way more channels than you can mix - indeed, you pick (in blocks of 8) your inputs and outputs from that "pool" of ports until you fill up your 32 in and 16 out.
Don't over think it... (and I'm not saying that to be smart - I'm saying it because I have shot myself in the foot a couple of times assuming things just had to be more complicated than they turned out to really be)
EDIT: 46:00 has a good discussion around multiple S16's that should also help you visualize.
