You can access your VM SuperHub at 192.168.100.1 because your default route is out through it (well, kind of, but effectively that's why).
If you're currently using 192.168.1.0/24 (255.255.255.0) and you want to also use 192.168.2.x, then you would indeed need to use a subnet mask of 255.255.252.0 which would give you a usable range of 192.168.0.0 - 192.168.3.0 (noted as 192.168.0.0/22).
Because of how subnetting works, in this case you can use:
192.168.0.0 - 192.168.1.255 with a netmask of 255.255.254.0
and
192.168.2.0 - 192.168.3.255 with a netmask of 255.255.254.0
(and you'll need to route between those two on your local router, and therefore have two IPs on its internal interface, one from each subnet) or
192.168.0.0 - 192.168.3.255 with a netmask of 255.255.252.0
Correct, that'll give you 192.168.0.0 - 192.168.3.255 . Just make sure you then change the netmask on all the existing devices as well, otherwise they won't see the new ones properly, and vice versa. Windows has its caring tendency to automatically fill it in as 255.255.255.0, which is nice, but potentially annoying.
You won't need to change your router's IP (I'm guessing 192.168.1.1 or .254?), that'll keep working just fine with the new subnet.
Thanks. Yeah, I'll just power cycle everything that needs it and tweak a few static IPs. I /think/ most are dished out as static by the router itself defined my MACs, but I'm sure I've got a few that a proper manual.
It's mainly because I'm going to making use of a number of ESP8266 devices and it would be nice to have them organised together in a separate range.
I'll hopefully be removing one RPi from my setup and replacing it with an ESP8266 at some point once I paint my desk and get my "office" back in working order.
Dunno if this helps, but my wifi router does 192.168.2.x, and my tablet can see local webserver @ 192.168.1.x (wifi & server both to same wired router)
driver killed while using autopilot was watching Harry Potter