Hello Ccalabrese, about your questions.
Can I use the Swisscom Internet Box2 for the TV Box and the Orbi system at the same time?
Yes, you can do that.
How do I connect the Orbi Set to the Swisscom router?
You connect the Orbi router to the Swisscom router via a network cable and the Orbi satellite then extends the Wifi wirelessly.

BUT

Unfortunately, in the past I had more and more problems with interruptions with the Swisscom Box+ and the Orbis on Swisscom TV, so I switched to the WLAN boxes from Swisscom at the end of last year and have had no more interruptions since then. Unfortunately, Swisscom doesn't make it easy to use secondpart products, but I don't want to assume that they did it on purpose.