lol, many questions indeed. as someone who has just bought all of this stuff, i think i can help.
"So I read in a previous thread that for direct dripping using my eGo to go with the LR atomizer. What the difference with that and the mega I see in the store?"
the mega atomizers are just bigger, they're the same diameter as your ego battery, instead of skinny like the 510 attys that came with it, and they come in standard resistance and low resistance, i got the low resistance ones, because lr is frickin awesome!
"If I get the regular lr atomizer are there cartridges for that or should I just go with a tank system?"
there are cartridges for the skinny 510 attys, and the mega attys in both cone and cylinder styles. however, carts aren't very good, you're better off using your atomizers for direct dripping, and a tank system or cartomizers for when you can't drip.
"Typically I just direct drip with my atomizer but I see that some are using cartridges (do they leak) or the tank system and are happy."
i haven't had any leaking issues with cartridges, but direct dripping is way better. the tank system hasn't leaked very much for me. if you can direct drip, do, i prefer it to everything else.
"Will my cone fit over a regular or mega atomizer? Do I need a drip tip for either...looks so."
your cone will fit over the 510 style atomizers, not the megas, as they's the same diameter as the big end of the cone. you need a drip tip for any atomizer you want to drip with (at a buck apiece, get one for 510, one for ego cone, and one for ego cylinder and be prepared for everything)
"If I want to try the tank system, do I need a special atomizer?"
yes, you need an eGo-T atomizer (the -T is for tank) and yes, it will work with your regular eGo
"Do I buy the tank cartridges separately?"
yes, look for eGo-T tank cartridges, they're usually blue, translucent and all plastic.
"Should I just go ahead and get a tank kit?"
you could, you'll have to weigh your options, the tank kit is easier to clean and refill than cartomizers
"Should I just stick with the lr cartomizers I have been using with success?"
IMO, cartomizers are great if you're sticking with one particular liquid, if you're trying a bunch of different liquids, they're a huge pain to clean all the time. if you fill them with the same liquid over and over, you only really have to clean them once they start producing less vapor and throat hit. tanks and cartomizers are both great options for when you can't drip, i've tried them both and can't really decide on which is best.
hope this helps
Jon