For drop-shotting on beds, you should probably use 3-4" between hook and bottom if you are on a boat. If you are on shore, you should make the length longer so you can keep it on the bed longer. Try using bright curly tail grubs in chartruese or white. That's what I have been using and I like it better than using white jigs.

For drop-shotting not on beds, as far as the length goes, it just depends on the lenght of the weed growth is that you are fishing.
If it is 4 inches then you should fish it with about 6 to 7 inch length.

If you get around to it, try the pig-n-jig. Las time I as there, there was these 2 guys that showed up near me and 1 of them made a cast right by this pump thing and he nailed a 5 lber first cast and then his buddy did the same thing and nailed a 4 on his first cast. I talked to them the next day cuz I was camping and they said that night they got abut 10 more fish each biggest was 6 for one guy and 8 for the other guy.

I can't help you as fa as scent goes, I am tryig to figure this whole scent thing out myself.

Hope this helps.