About to install but I notice it's in the middle of a run. The old outlet has two black / whites. Do I just put all three blacks and all three whites together? Yes it has ground. I was just worried...

So I have the new S4 mesh up and running. Since there are two ports on the main S4 (the one plugged into router) can I add a dumb switch to one port? I have a couple of devices I have hard wired into...