I prefer to use weighted flies instead of split shot. As to where i put the weight it really depends on what i am doing. For streamers where i am casting distance to cover water i put the heavy fly on the point and the dropper on a tag above it. If the fish are hitting short i will cut the tag dropper off and add a smaller unweighted fly off the weighted streamer bend ( a large soft hackle works great). Sometimes when fish are short striking and i am casting distance i just forego the dropper and try a smaller streamer. For nymphs the best strike detection comes with the weight on the point and and the unweighted fly on a tag above it. if the fish are taking aggressively (or i am trying to find the fly of the day) i often rig the weight fly on top with two unweighted nymphs tied off the hook bend of the fly above it. When i fish like this the weight fly is usually the largest hook size and the point fly is the smallest hook size. Having the weight on the point with a tag dropper or 2 above is the least prone to tangle has the most controlled drift and best bite detection. If i am helping a newer fly fisherman adjust to fishing 2 flies i always rig him with as small a tungsten fly as conditions and hatches dictate on the point with a small fly on tag dropper above. I make sure he know how to roll cast or water load cast and they are usually amazed that they rarely get tangled