Using the vanilla install of nQuake...
C:\nquake\ezquake\configs\config.cfg doesn't exist, but it gets created upon first/initial startup of ezQuake.

Default controls look find:
Q or CTRL - super nail gun
E - grenade launcher
R - lightning gun
mouse2 = rocket launcher + immediate shoot

some interesting new team-talk-binds: X, C, V, F, G

Coolio. After messing around with the settings & graphics I decide I want back to defaults. So I click on reset back to defaults.
Nope, it didn't change the graphics.... okay...
and now single player is messed up.
Single player loads up like a multiplayer with no monsters....

Weird.

the default configuration is inside a pak file. you can retrieve it.
Go to c:\nquake\qw and open the file nquake.pk3 with a zip program, like winzip, winrar, whatever
there's the default.cfg on the root. extract it to c:\nquake\ezquake\configs and rename it config.cfg

NOTE: backup existing config.cfg if you like.

now run ezquake normally. it now has the default config.