Hi C99, Welcome to the ECF. Ok So you are looking for a vv device with the capability to run 6v. I have a lavatube mini as my backup device. It works well on standard resistance carto/clearos(including the vivi novas) through the entire output spectrum(3v-6v) But on the rebuildable atomizers that I have been getting accustomed to as of recent months it doesnt have the current available to run those(my
coils measure~1.9ohms) at high voltage(4.8v+). I know that technically it should but I can attest that it does not.
Amperage output is your friend in this area. If you can find actual tested amperage capabilities for the specific devices you are looking at this should hold as much weight in your decision as every other factor, if not more in my opinion. So depending upon your immediate needs there are a few very capable units available.
I also have been eyeing the Anyvape CVI mostly because of the 4ampere output limit because if I want to run something on my backup device I expect it to run what I want to run at that moment.
This is my two pennies on your question.