Here's a guide that's been posted elsewhere on this board regarding matching ET-2 tonearms with cartridges:
I'm not aware of a boron arm wand. The stock arm wand is aluminum. The lighter one is the carbon fiber and the heavier one is magnesium. Assuming you have the single leaf spring and the carbon wand, you'll want to use a low mass, medium compliance cartridge.
I use the AT-OC9XML on my ET-2 tonearm. If I had the funds I probably would bump up to the ART9XI. I'd love to try a London (Decca) Super Gold someday, but those suckers are hard to get dialed in on many tonearms, especially a linear tracking one on a suspended turntable.