WPS makes the router run in wpa2 mode for most routers.
Still both WEP and WPS are very bad things to even think to use. WEP is extremely easy to crack, it is almost a invitation to script kiddies to try to hack you. WPA2 is good security but if you use WPS that feature will give out your really good WPA2 password to anyone who finds the 10digit WPS code and that can be obtained in a few hours....and you can never change that 10 digit code.
You need to leave WEP disabled and also disable the WPS feature and manually set the WPA2 password.