I usually go weightless with a 3/0. Texas rigging works best when you peg the weight. Carolina rigging is best when fishing a slope. But, like everyone's saying, there's really no wrong way to fish a Senko. They cast like bullets and the fish are crazy about them. Just don't expect them to last.
wacky rig - Gamakatsu G-Finesse Series Wacky Jig Head (whatever weight the situation calls for but 1/16 is my preference if i want almost 0 weight)
texas rig - 3/0 or 4/0 gamakatsu skip gap worm hook. i usually only fish senkos when skipping baits so these hooks are a huge help in prevent the worm from sliding up and down the hook shank and tearing the bait up.
Totally agree with you Sam on the skip gap hook, regular EWG hooks are a pain in the ass when you are trying to skip, every other cast you have to reset the bait, not to mention your bait doesnt last as long.
For wacky rig I usually use a weedless 2/0 wacky rig hook I dont find any problems with the hook size and shy fish so to speak, I have also used 2/0 demon circle hooks believe it or not they are pretty much fool proof even if the fish bites and you are not paying attention you hook him 90% of the time