Don't use a charger that wasn't designed specifically for the batteries you are putting in it. There is a real risk of fire, but you're mainly going to destroy the battery and/or charger. Only use your greensmoke charger for 808D-2 batteries.
I use a 401 (same as 403, just longer battery life) with 100% VG. I use atomizers. There are cartomizers available for these M series batteries, but not many. I think there are two. The best are probably the CE2 cartos, but there are those who think CE2s are poorly designed. Vapor production is lacking with these models as they are older technology, but they taste great. I don't need heavy vapor production, I smoke analogs without huge clouds of smoke. 15-18 puffs off a king size is more than most get, so I guess I take small drags. The cool thing is that the M series is a very small diameter. It's the same as my king size cigarettes. I make my own using tubes, so they are a bit larger than commercial smokes.
808s are reported to give more vapor than the M series. They are also new products being developed for the D-1s. You get a lot more color selections, and cartomizers are plentiful. They are slightly larger than the M series, but no larger than 510s. I do not know how they do with high VG liquids, but I imagine they would work well if the cartomizer can wick the VG. Cartos that easily flood with PG may be a good choice for VG.
The eGo is a large battery version of the 510. If vapor production is your primary desire, this is probably the unit to go with. It's quite a bit bigger than a cigarette, but not overly bulky. It has the widest selection of cartomizers available, and can be used with attys for dripping, atty/cart combos, and tank systems. There is also a mega version that uses large diameter atomizers and cartridges. I suspect that mega attys can be used longer before they need to cool down, but you'd have to ask someone who owns one. The Riva is a clone of the eGo, and has it's own rabid followers.
I currently just use a 401, but my wishlist includes: 403 auto batteries for hands free vaping while I do housework, a KR808D-1 setup with PCC, and an eGo. The 401 will be used for different flavors (testing and just to enjoy some of the more decadent liquids). The 808 will be my all-day vape when I'm on the go. The eGo will be my all-day vape at home or whenever I can carry it conveniently.
I have no need for a mod, just as most people have no need for a modded car like from The Fast and the Furious.
If you need more thoughts, ask away.