Product AC1750. Network Key Password

> I was wondering if all of the R6700 WiFi modem passwords are [...]

   No.  That "<dictionary word 1><dictionary word 2><decimal number>"
passphrase should be generated uniquely for each device.  (And an R6700
is a router, not a modem.)

   If you don't trust it, then choose your own.

> [...] I had a increase of usage and trying to make sure it was just me
> and not someone who tapped into my WiFi. [...]

   In the router's management web site, watch: BASIC > Attached Devices?

   Enable access control?

   Visit http://netgear.com/support , put in your (actual) model number,
and look for Documentation.  Get the User Manual (at least).  Read.
Look for topics like "Specify Basic WiFi Settings" and "Control Access
to Your Network".