Permanent Connection to App?

Hello, I have a question:
I am still waiting for my P1S printer and until then I want to setup my WLAN connection in the basement of my house. In the Basement where I want to setup my printer, I have no WLAN signal but I want to use the printer with the Bambu Handy App to check my prints while I am not at home.
With my current Prusa MK3s+ I don´t need a WLAN connection

I want to use a mobile WLAN Router with a SIM card because (as I said) I don´t have a wlan signal in the basement and no possibilty to connect it to lan or get this signal in the basement.
I tried wlan extender before but if i don´t get a signal to extend, this device don´t work for me.

Anyways I was wondering how much data consumption the printer needs, maybe someone has some numbers and experience with this too.
Here in Austria I can get a SIM Card with about 10 or 20 GB a month for a few euros…
I think the printer is not connected the whole time to the Bambulab Cloud, I think when you open the Bambu Handy App it establishes a connection to it, the printer then connects to the cloud and starts transmitting data. Is that correct? In this case the data consumption would be pretty low…

Maybe someone has some experience with this.
Thanks and best regards!