I've been using my Chucks at 3.7v since September.
Completely happy with that setup and feel no need to experiment further.
I'm still using my standard 510s for when I go out for the evening.
But I was not satisfied with the vapor output on standard batteries after using the big 18650 batteries.
So I went out and got some LR atomizers which I now use with the stock 510 batteries.
WARNING: You are not supposed to do that, but it's working for me so far
As far as juices go, I don't have one favorite liquid...
I have many favorites depending on what I feel like having...
--Tasty Vapor Caramel Popcorn
--Nhaler High Voltage 555
--Backwoods Brew Malty Toffee
--Nhaler High Voltage RY4
--Tasty Vapor Tastyfinger
--MyFreedomSmokes Keoke Coffee
I also have a couple dozen other flavors that I use much less regularly than the above.
But when I want one of them, it is my favorite flavor at that moment.
I'm still evaluating a few different flavors from the following...
--Backwoods Brew
--FreedomSmokeUSA
--Ms T's Bakery
The Chocolate Biscotti from FreedomSmokeUSA has a chance to make my list of top choices.
And the Applewood Tobacco from Backwoods Brew also has an outside chance.
The rest I am just deciding if I want to keep them around or not.
Some that I am definitely keeping for infrequent use...
--FreedomSmokeUSA French Toast
--FreedomSmokeUSA RY4
--Ms T's Pizza
I am pretty sure all the other Ms T's juice are not going to stick around much longer.