For a cheap mod with great battery life, the 100W iStick is decent, but it's bottom of the barrel for quality. The parallel batteries give you lots of run time between charges though, and it's pocket friendly. Only $30, but you get what you pay for. I got the RX200 a few weeks ago and have been super happy with it. It hasn't been out long enough for anyone to really comment on it's longevity, but it's the best value for your buck these days. 200W, all the TC modes, small size, and only $40. I don't use prefab coils, so I can't offer much advice on a tank unless you want to build your own coils. When I did use prefab coils, the only sub-tanks I really liked were the Arctic and the Atlantis. Neither of them ever leaked on me. The Arctic had better flavor, but the Atlantis coils lasted longer. You can grab either of those tanks for around $20 or less these days since they are last years tech.
Regrettably I can not give much advice as I haven't reached the 100W vapes. In addition I cannot think of any mod and tank which may meet your criteria, especially with regard to it's portability. There are plenty of small mods that could feel comfortable in the pocket, but I believe most of them to max out at around 75W. I'm sure other members will come up with something. Hang in there!
