Falkor - you're right, streamers and standards won't cause problems when creating a pretender for MP. Basically all mods which don't affect pretender design are fine. When the game's actually running though, you won't be able to use the nod - the set of mods you use in an MP game is always the same as the host, and Dominions does this for you.
Yeah. When you set which mods you want to use in "Mod Preferences", you're actually just choosing which mods to use for any new games you create. You have no control over what mods are used for games which have already started, whether SP or MP.