[est31]

Of course in physical security, for every protection there's always a way for attackers to counter it. But it gets more and more costly each time. What I wanted to say with my comment is that off site backups do have value (compared to say cloud based door locks which don't have any advantage over internet free approaches).

For 1 and 2, ideally you'd avoid WiFi cameras for the reason you stated and use cable based ones and put everything into view.

To 3, actually this happened recently in my country Germany where they stole crown jewels of one of the german states. The alarm system died and allowed for silent entry but the CCTV still worked (no idea why it worked tho, maybe backup power for CCTV only but not for the alarm?). Ideally both your CCTV and alarm system run from some way of backup power.