I've found nymphs and streamers work best in really cold water. Mostly nymphs though, good luck.

Depends on which waters you will be fishing. Most tailwaters will require size 20-24 midges. Don't be afraid to run a slightly larger nymph above your tiny dropper. The fish will generally come to look at the attractor fly, then take the dropper. My typical rig: 9' 5x tapered leader with a size 18 copper john, then 20 inches of 6x to a thread midge or emerger like an RS2 or WD40. You have to get it right in front of their noses in the winter so play with weight and indicator til' you have it dialed. I also like to fish big white weighted streamers like zonkers and bunny tails.