That would be both from the device and the router.
On you Windows Computer see if you have an IPV6 IP either by running
ipconfig /all via cmd or by looking at your network properties under Settings.
Not at all.
The only problem is that it's adding an additional possible point of failure within the whole network.topology as in "another thing that can fail".
Not this one as this is an ADSL modem (old school, phone line dependent).
You would need another router that has a WAN port (where you would connect a LAN port from the Modem/Router combo).
It does take a bit of configuration though as you would have to disable the wireless in your Netgear too (or leave it on with different name and password - but if you can disable it, disable it as it will be less noise on the 2.4 and 5 ghz ).
You next cascaded device would become the primary device to serve all the network.
With a $300 device using it as a bridge ... you'd be better off selling it or returning it and using the combo i was talking about here ...