You're comparing different types of batteries (protected vs. unprotected). Your Kanger, MVP2, and Ego Twist are all internal batteries and are protected meaning they protect against common dangers, such as overcharge, overdischarge, short-circuit (overcurrent), and temperature. These batteries are safer to use are less likely to ignite and cause personal or property damage, a phenomenon known as "venting with flame." The Hcigar Nemesis is a mechanical mod and uses external unprotected batteries that does not have the protection against the aforementioned problems and you'll need to keep a close eye on it with a voltage meter.
Mechanical mods are commonly used with RBA's and RDA's (rebuildable atty's/drippers) and can handle sub-ohms, whereas most protected mods/batteries can't use anything below 1.3 ohms. If you decide to rebuild you'll need an ohm's reader. There are ohms/voltage readers. A word of warning if you do decide to get into mechanical mods and such, do a lot of research on battery safety and guidelines. Do the same if you want to rebuild.
I hope this helps.
Ps. You can build 1.3 ohm and up atty's for use on a protected mod if you want to try it out.