Sorry to say this, but to my knowledge, there is no Bluetooth and you can only communicate via Ethernet (and indirect via WLAN). And of course USB data stream. So your tablet can communicate via WLAN and your server has to have some Ethernet connection which has to be connected to the WLAN.
There is an offline mode for the server, which seems to only block communication from the server to external sources on the Internet. So you can play without Internet connection, but you should know the IP address in your network and this network has to be active.
And the biggest disappointment might be, that you cannot just play music from the Innuos server to your iPad. It is supposed to have one defined player (your DAC) via USB. There is an option to access from sources like iPad, TV or whatever via UPnP .... sorry, am not a specialist for this.
Usually, you will connect to your NAS (network attached storage = file service) like this (UPnP) for playing music.
Hope somebody else can tell you more. I just use with my DAC ...
Good luck. Don’t be disappointed, if it works in a different way, than you expected, but it is definitely an excellent device for what it was intended for by the designer.