Isn't the 40T a 30A and the 30T a 35A cell?
Oops, my bad. The 40T is 25A 4,000 mAh off Mooch's chart. The 30T (which I don't have any of and hence my recollection was incorrect) is 35A 3,000 mAh. Now that Samsung has a 30A 2,000 mAh 18650, the 20S, I got them confused.
4,000 mAh gets me well through a day with say a Topside with a 10 ml squonk bottle as I only vape maybe 7-8 ml a day. Two VTC5A's may give me 25A each, and 2,500 mAh each, but it's not a 100% "efficiency conversion" for want of the proper term. Add them together and in practice you'll end up not a whole lot more over 4,000 mAh anyway. I know we can get into wH which is probably the best way to compare side by side, but to me the difference isn't all that much while the form factor is definitely a difference. If I want to go to 80W on say my Topside, the 40T is really sufficient, although I'd probably get a 30T just to feel better despite it being regulated. We all have our own safety zones.
All of my regulated squonks are single 21700 mods. I can also use an 18650 if I'm stuck without a charged 21700 around. And a 21700 mech squonk with a 30T gives you some decent build options unless you're into ultralow superconducting territory which is essentially a teeny step away from a short. I mean a 0.12 ohm coil will draw 35A which is 147W. I can't see anything beyond that territory as a place I personally want to visit.