You should basically only install WeiDU mods, unless you know what you're getting yourself into. All mods at PPG are WeiDU, so you have nothing to worry about. As for installation order, some mods are designed to patch other mods, so naturally you'd want to install them last. Virtue is a good example of this.
Fade and Cailean are highly likely to be compatible.
I don't remember where I saw it, but on some forum on some site someone was having mod problems. He had lots of mods installed and someone gave some very nice information about installing mods: the order in which to install them! People are either thinking "oh yeah, I remember that!" or "wow, this kid is off his rocker".
But it said that you should install all WeiDo mods last (or was it first?) and then there were another kind of mods he said to install second, and than last. I was just wondering because I've been un/installing quite a few mods lately (getting ready for Cailean to come out!) and a couple of them are WeiDu mods. I just want to be sure that there isn't anything wrong when I go to play the game so.. does anyone know what I'm talking about?