Wouldn't this only be applicable for one device with multiple accounts though, as opposed to multiple devices?In the end I used bitdefender
Have a look at family pack.
I had a bit more of a play with things. I booted up my 2-in-1 and it connected via dhcp and had internet access. I then put in a different static ip address and it still had internet access. I then put it back to dhcp and connected to my other Gargoyle router. Changing to the static ip address killed the internet access. I then thought that I might be getting different behaviour on the different routers (Archer C7 and Netgear WNDR3700). So I changed back again to the Archer C7 and repeated the process there, but this time it killed the internet access after entering the static ip address. I'm not sure why it didn't do it the first time but did do it the second time.