1. Can I use a light power rod for a drop shot rod? 

2. Benefits of fast vs x-fast? Does it really make a big difference. Many of the x-fast rods that I like seem to all be 1 piece rods. I would prefer a 2 piece rod. 

3. Does the size of the bait have a big influence on the rod power? I plan on drop shotting something as small as a fly or two on my line to a 4 or 5 inch finesse worm. They would be on similar sized hooks. 

Drop shot is really just a terminal rig. If you're vertical jigging , depth , cover and fish size factor into Rod power choice. A ml is more appropriate in most cases I encounter. Since you're not loading the Rod for long casts you can use a weight above the ratings safely and still have the lite bite detection and presentation of a lighter power Rod. The XF action is nice for reel setting the hook but either will work.