duplicate players from same ipaddress

Hi @Kekora,

I don't think IP addresses have anything to do with this.
In fact I still do not see the issue here. I do not see how and why you are getting same nickname on two different clients if you do not set the same nickname from those same two clients and you do not return it in the custom authentication response.
What are the UserIDs for those clients? If you do not set one explicitly from client or from web server then Photon Servers will return a random GUID. So I doubt you will receive two identical ones.

If you want to have a single connection per user then you can implement it in your custom authentication. Just send credentials per user and "start"/store a user session on web server. You can make use of WebRPC and WebHooks to end the session (know when a user has been disconnected to avoid clients being stuck due to endless session).
You can do custom authentication with Photon Chat.

Having same playerName from Editor and standalone build on same machine is expected as you're loading and saving same shared PlayerPref. You can avoid this by saving Editor playerName separately. e.g.:
save:

string userID = Username_field.text.ToString();
#if UNITY_EDITOR
PlayerPrefs.SetString("editor_playername", userID); //set it for loading in next scene
#else
PlayerPrefs.SetString("playername", userID); //set it for loading in next scene
#endif

load:

public void OnJoinedRoom()
{
#if UNITY_EDITOR
PhotonNetwork.playerName = PlayerPrefs.GetString("editor_playername"); //set our player name
#else
PhotonNetwork.playerName = PlayerPrefs.GetString("playername"); //set our player name
#endif