Well, from an anti-freeze scientist's perspective.....
1. Distilled & de-ionized both remove the ions, which is what you want to do. Distilled is 100% pure water & de-ionized is 99.9% pure water (no ions, some dirt)
2. You do need to run some type of anti-corrosion product (e.g. water wetter type stuff)
3. Water Wetter has very poor aluminum protection (I've tested it personally). Works just fine for iron heads/block
4. For aluminum heads, I suggest either Royal Purple or Lucas (formulas are identical except for color - I've analyzed both myself)

Hope This Helps!