First of all, thank you for mentioning "VMU"! I hadn't heard of it and I had to look it up. So, a new VV
mod!
Depending on the type of atomizer or cartomizer you use on a 6V mod, the intensity of the vape may be similar. I need to dabble in an Ohms Law formula a bit to say more about this. The intensity of the vape is the
power, which is measured in
watts. But watts are not a property of either the battery or the atomizer, but are derived from both. Specifically:
Watts = Volts X Volts / Ohms [or just let this online calculator do the math for you]
If you currently are using those 2 ohm cartos on a
true 3.7V device (i.e.,
not an eGO), such as a Kr8 battery or mod, then you are experiencing 6.8 watts (in the middle of the 6-8 range often regarded as the "sweet spot"). If you are vaping them on a ~3.3V eGO, you're getting 5.4 watts (not bad).
If you were to try using those 2 ohm cartomizers (please
don't) on 6V, you'd get an overwhelming, juice burning
18 watts ... and a carto-frying 3 amps current.
And this is why "HV" (actually high-resistance) atomizers were created. For example, a 4.5 ohm HV atty on 6V yields 8 watts and only 1.3 amps: ahhh ... life is good!

So match the atomizer (or cartomizer) resistance with whatever voltage you are vaping. [I talk more about LR and HV attys (and this volts/ohms/watts/amps stuff) in
this article.]
Variable voltage mods (like Totally Twisted Texas'
VMU Innovate) enable you to use
any atomizer or cartomizer to achieve
any watts intensity ... and to tweak that intensity to fit your e-liquid and mood. They really are a great concept.
Some of them (like the VMU Intensity and the Big Brother) are
box mods, which will feel very different in your hand, if you are used to a tubular PV such as the eGO.
For more information about 6V and VV mods, check out
The Wonderful World of Mods in the ECF Library, especially
this post.
And no, I don't know of any fat batt (i.e., eGO-type) that is 6V.