Two new guides for NWN:EE multiplayer have been released by the new Neverwinter Connections.
NWC Multiplayer Connection and Hosting Guide - this is a step-by-step, illustrated explanation of how to use NWN:EE in multiplayer (MP) mode. It walks through the process of both joining Internet games and hosting a game on your own computer. No prior experience necessary.
The NWC Quick and Dirty MP Roleplay Reference is designed to help orient those new to the multiplayer interface, as well as providing a common (optional) reference point for in-game behavior.
Between the two of them, people should have an accessible way to get all the info required to play and host MP games.
The Old School NWC Roleplayer and DM guides by Gruush and Lazybones are also now available (with their permission) on NWC’s multiplayer resource page, along with a number of other community links. This includes links to lists of multiplayer and DM-friendly modules on the Vault.
Community feedback, suggestions, and errata for the guides are welcomed.
#1 - depends on what module you’re looking at. The Vault module descriptions are usually accurate in terms of whether they will work in single player mode, multiplayer mode, or both - although there’s no guarantee. That’s one of the reasons NWC put out the multiplayer (no DM required) mod list and the DMFI has the DM-friendly mod list, where they’ve all been proven to work by direct experience. Naturally things like PvP mods or DM-only mods won’t actually work as intended in single-player, although technically you can still play them.
#2 - the Multiplayer Connection and Hosting Guide linked above walks through how anyone can host a game, either as a player or DM.