I'm not one of these players who plays with one eye on the framerate counter. I judge these things by how the game feels to me. All I can say is that it doesn't feel as though my game slows down when I use these mods.
This, I only use Immersive Armors out of the three you listed but it doesn't affect my game as far as fps feels. If you have fps trouble it is most likely due to high res texture packs, poor RAM or graphics card, or it can even be running stuff in the background like Firefox (What I use, can be any internet provider) other games or apps. For me you can Ctrl Alt Del and pull up your task manager and end unneeded processes. I always do like Itunes plays in the background for some reason or openoffice crap.
Of course having 100 NPCs in your view with these mods would kill your game

But armor and items shouldn't be your source for cutting FPS loss because in my experience they aren't the problem. I don't know what SkyMoMod is so can't help you there.
Edit:

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