Guys if I may wade in here:
First of all congrats on not smoking cigs anymore. 35 years for me battling that addiction until I discovered what was, for me, the miracle of modern vaping. My discovery was several months ago, and am also reaping all the health rewards just the same as anyone that managed quitting cold turkey. I was a pack a day of reds type strength cigs.
FWIW My Arsenal:
Subtank Mini 4.5ML Teamed with an Athena Envy 22 3400mah regulated mod
Pricey battery by ecig terms, but the caged design for all day made that justifiable for out and about IMO.
I tend to use the 1.2 ohm coils. Using about 70.30 VG / PG (7mg nic) I get plenty of vapor, and enough nic hit. You can use the .5 ohm coils, but I don't care about huge clouds and they just burn the juice and battery quicker.
I also bought a clone of this from Fasttech, and really found it just as good for way cheap.
I also use the included RBA to build my own coils.......way quick and easy, works just fine and amuses me to save a few pence now and then when care.
With the 1.2 ohm coils I vape at around 18 -22 watts, and find it lasts me fine. I keep a spare tank / 10ml dropper bottle handy too, but really no issues with getting through too quick for me.
Nautilus tank / Innokin Coolfire 4 40 watt 2000 mah mod (mod = regulated battery if anyone wondering)
This 5ML set up I use about 60 - 65% VG, and rest PG juice wise. Coil wise I use a 1.8 ohm coil, and vape at 11 - 13 watts. This is a v long lived, between fills, method I find. Also very much an out and out mouth to lung (cig style) draw, but can veer enough direct lung hit when mood takes (opposite to the subtank). Nic wise I make this with about 12mg nic content (less vapor on the pull).
I also bought a 20watt istick clone, and nautilus mini tank clone off fasttech. For now and then when want cheap as might lose it's just fine, and just fine anyway, especially at $20 all up..amazing how they do that.
I mix my own juice using pharma grade PG / VG, and real good quality flavourings / nic juice. Cheaper than buying I find, quick and easy and way better quality also - IMO.
If any of that helps anyone stop smoking cigs fantastic. May also help with the larger tank capacity question, as my question is are you sure you need it with what I have said in mind. If still need it I have heard the 7ML subtank is a good 1, but never having tried it can't say anymore.
Now please excuse some paranoia: Anyone new to vaping please do take your time to understand Ohms law. This is especially so if you go below 1 ohm coils as you can very easily make a pipe bomb if you do not, but do understand it anyway. Also take the time to know just how dangerous strong nic juice can be. Stay safe and GL to all:)
EDIT: Battery drain rate capability especially if chasing low ohm huge clouds is also be vital to understand. Don't let me put you off though. A sensible regulated mod with a sensibly matching tank / 1+ ohm coil from a decent place versus smoking .........no brainer to try, IMO.