My SIM is from Swisscom; I am happy with the performance of the device and also watch TV on it.

Hello
To answer the question, I had Sunrise. The connection speed was fine for me when it was available. But most of the time the wifi didn't work properly with this router.

The card should work. The connection of the device is good, but of course also depends on the availability of the network provider used (apparently Salt in your case).

I get around 15mbit upload and download in Neuenegg (Canton of Bern) and Hitnau (Canton of Zurich).
Of course, this can change depending on location and utilisation.

Hello I don't know I haven't tried it yet