You're going to struggle to find something you can twiddle in your fingers that does what you want. Automatic batteries are a cigalike feature, I don't think it exists for more advanced equipment. You will get used to buttons very quickly, it will become natural.
Regulated tube mods (cuban cigar shape) are not very popular these days, there aren't many that will go over 40W, which is not enough for some of the new subohm tanks. They're not discreet either, you're generally looking at 22 mm width and at least 100 mm long. What do you mean by "powerful"? 40W is not a lot in the current market, where 80-200W is becoming standard, but compared to a cigalike 40W is massive.
I'd say discreet and powerful is box mod country, iStick pico perhaps?