1) i dont think i want anything more than 900 mah, cuz im in miami and we wear tight jeans here. Lol, I just dont wanna lug around something bigger than a 900 mah, if i cant stick in my pocket or i'll lose it.
Y'know, I thought that too, at first. With my egos, I've got 650's, 900's, and 1100's. The 650's seem impossibly small to me right now -- I use the 900's and the 1100's all the time, and trust me, they fit fine into the pocket of my jeans (although the 1100 has a tendency to stick up slightly above the top of the pocket). If you've got an ego 650mah battery, imagine about another half-inch of length (no increase in width) for the 900, and about 1.25" longer than a 650 for an 1100, rough figures. But if an inch and a quarter converts into almost double the battery life, I think it helps.

Diameter's the same for any ego-type batteries.
Now, in terms of mods, the batteries go into the mod, so what I think you're concerned about is the size of the mod. My lavatube-type is like... mmm... a narrow-handled screwdriver in size. Basically, set a quarter on the table, put your ego batt on top of it, that's the diameter difference in going up to a lavatube. So if you're concerned with the diameter, that particular VV may not work out ideally.
However... there's the option of box mods. Maximum Vapors (one of the ECF vendors) has a box mod for VV that's around $60, but it does not come with the batteries or charger that need to go with it, so you will need to pick up those (either from another vendor or from him, whichever). And those are no worse to stick into your pocket than a pack of cigarettes would've been.
2)Price range under 60, because even though it may be compact, im probably gonna lose it. Your right, I think I am happy with just three vv settings. I find that I vape between 3vts on attys and 3.7 on carts
You'd be surprised how much your thinking on that may change with VV mods. I was perfectly happy with how everything acted/tasted until I tried one of my bakery juices (a cinnamon roll flavor) at 4.6 and was hit with the rich, decadent taste of buttery cinnamon roll to the point where I wondered if I could chew it.

But it's still trial and error to a point to find what works best for you. Most of my juices, I tend to use in the 3.6-4.4 range now, and I'm perfectly happy there. Higher voltage does wonders for tobacco juices, I've heard, but I haven't actually played with that (I'm fine with my tobacco juices at lower voltage). The range I'm in right now means that I still can use my egos while on the go, but I can go for a richer and more flavorful vape at my desk at work or at home, where whipping out a screwdriver-sized PV won't get me strange looks.
3) You know thanks for bringing up the carto tanks. I totally forgot about those. I would imagine that those cartomizer mini tanks would be be hotter than those actual tank set ups. I have tryed the fluxomizers on clearomizers. Great vapor but not too happy with the warmth of vapor @2.3 ohms and 4.2 volts.
Not necessarily. For my ego batts, one of the best purchases I made was Riva-T tankomizers. They're nicely contained for on-the-go vaping, look good, and have screw-on caps that look like pen caps (which makes them less obtrusive if you tuck them in a pocket). But with those on a 650 batt, I notice my warmth drops rapidly during usage as the battery gets discharged, and it's almost a cold vape right before my batt needs charging (not necessarily bad, but not much vapor at that point). The Riva-T's run at about 3 ohm. On a Riva-standard battery instead of the ego batteries (same shape/design, slightly higher voltage), I find that the Riva-T works even better, because the Riva batts tend to run at around 3.7 standard where the ego batts are a little less (3.4ish).
Still -- for consistency's sake, you still are going to want to invest in a VV mod, if only because the batteries in 'em hold out a lot longer and thus produce a more reliable hit over long-term. It's probably something you won't use while out on the go as much, unless of course you're going to a vaper meet, at which point everyone'll be whipping out the wild mods.
