The key to true stealth vaping (i.e. a satisfying vape with almost no vapor) is lowering the power and jacking up the juice's nic content to make up for it.
My go-to device for stealth-vaping in places you'd never expect a vaper to vape (such as long, boring company meetings) is my Gecko 10440 mech mod with a sawed-off Smok Mini RDA: it looks like a shortened pen - meaning I can keep it on the table, and it looks like I chew on a pen when I vape - with 18mg juice. Being such a low power device (roughly 5 watts with a full battery), it's not likely to make huge clouds