(1) Ben Harrison's Wizard Hats were made as a cloak. I can see the advantage in that the player can take them on or off, but it would be nice to have such a thing as a Head Aligned VFX. Is this available anywhere? I can't find it on the vault, but I vaguely recall reading about just this thing showing up.
This sort of thing has shown up. I converted that hat to a head VFX for my PW. I just haven't released them publicly.
(1a) Project Q also did Cavalier HAts the same way - cloak model - is it generally accepted that a cloak is the better implementation for hats? Why?
For each hat VFX, a new model (and line in visualeffects.2da) is needed, and each hat needs a new model for each PC race (except half-elves, which use the human ones) and gender. 12 models per hat. Then you need to make a whole new model for each color you want, since you can't alter a visual effect's colors in-game like you can a cloak. I also converted the cavalier hats to VFX for my PW.
Also, if you want to be able to change the color of specific parts of the hats, that's more models (another full set of 12 per color). For the wizard hats, I have separate VFXs for the main part of the hat and the band around it. For the cavalier hats, the hat is one VFX, the feather is another.
It adds up to
a lot of models and 2da lines. Nowhere near as easy to implement as adding a cloak or two, which do not require custom scripting.
(2) visualeffects.2da is there an explanation online for what each column does? I'm unclear on some of these impact nodes.
Answered above.
(3) In the visualeffects.2da, there are vfx labeled with a "SCENE" prefix and have tiles as their impact node. Can these VFX only be used on these tiles? If so, thats gonna be tedious to take a lookk at these and determine if I want to use them. Anyone have clues to share about some of them?
The "scene" visual effects use the tile model as a visual effects model. By applying these to a plain, flat area, you can use them to fake tileset features. If you do a search for TileMagic, you should find ways to use these for things like filling a room with a few feet of water, making a pit in the underdark full of lava, or even making other types of tile features appear out of nowhere. Visual effects don't use the tile's walkmesh, so you can wade right through such water or lava (or tree, or whatever).
Visual effects can be any type of model. Those "scene" ones just happen to use existing tile models.
(4) Likewise there are the cage related visual effects that appear to have a placeable reference as an impact node. How does that work?
Same way as the "scene" VFXs. It's just using a placeable model as a VFX. You can apply it at a location or on a creature. If on a creature, the cage would move with that being. If applied to a location, it would sit still. But...it wouldn't block movement, so you'd need some other way to hold a "caged" creature in place.