Hi Sara
I finally climbed aboard the iStick train about 6-7 weeks ago. I grabbed the 50W, not necessarily for the power, but for the battery life. I'd been using VV3s and MVP2s most of last year, but I was charging the MVP daily or the VV3s multiple times a day. I liked the 50W so much I grabbed a 30W, and I love it for its size. It's not much larger than the VV3, but compared to the MVP or my iPV Mini, it weighs nothing!
Tanks - ooh-wee - that's a tough one. I haven't tried very many. I started with a bunch of EVOD tanks and then "graduated" to ProTank 2s (the heads are the same). That's all "old tech" now
I have a couple Nautilus (Full and Mini) tanks that are nice. Resurrected them recently after a long hiatus. I had a good few days run with them, but now they're acting a bit weird on me (I'm thinking my VG level in my juice is too high for those tanks

) They have a tighter draw (which can be tweaked with the airflow controller) which may be more reminiscent of your cartos. I also have a couple of Kanger Subtanks (Mini and Nano) which have a very airy draw. Simplicity - I like the Nauti and the Subtanks because I can just drop in a coil and go. I can rewick and/or rebuild the Kanger OCCs.
I hear lots of talk about the Melo or the GS Air, but I've never tried either of these. The Melo is a sub-ohm tank; the GS Air uses a 1.5 ohm coil (I believe).
HTH