I can't say anything about 5v, because I don't use one....but as a recent convert to mods, I agree with gb and say the REO mini.  I also agree with Firefly....though my hubby, a massive mod collector, would be mortified to hear me say this....I think the metal mods are much more durable.  I use the REO mini which runs on a 3.7v 14500 battery, has 3ml bottle for juice, an LR atomizer and drip tip.  That's it.  I love it because its small enough for me to hold and operate comfortably, and it is simple to use and maintain.  And that was a big deal to me cause I'm lazy.  Anyway, I wish you well on your qwest.  I'm sure you'll love the mods once you try them.