m6000w and Rise ,
IMO ,this thread seems to have veered a bit away from helping you get the equipment you seek . If money isn't an issue for either of you, ProVari V2 is a top notch vaporizer that will perform the same from the beginning of battery insertion until the battery is discharged.
The pv, be it ego twist, ProVari V2, kgo,go go etc . supplies the power to the liquid delivery system.
I would suggest you both go to you tube. In the search box type in "pbusardo provari". Watch video.
Then type in "pbusardo ego twist" . Watch video.
pbusardo is a highly thought of ,if not the most highly respected reviewer in the vaping community.
After watching his reviews,you will understand the pros and cons of each device.
Liquid delivery is a whole other factor in the vaping equation. There are atomizers,cartomizers,tanks etc ad nauseum .
I like the Vivi Nova. Easy to fill. Easy to maintain. The atomized heads are easily replaceable and also rebuildable should you be so inclined.
pbusardo has reviews on the Vivi Nova also.
There are so many vapers with different preferences that it is going to be hard to pin down exactly what is right for you.
It isn't often Provari's are recommended to beginners but there is nothing hard about them . They are expensive ,durable functional and maintain their value . Should you decide to sell , expect to lose no more than 10% of its cost,if that.
Atomizers are a good thing to have on hand to taste test liquids before filling a tank and finding you do not care for the taste.Every vaper should have at least one.
IME, most spend a lot of cash finding liquids they really like. Don't buy large quantities of any one flavor to begin with unless you already know you like it. Try smaller bottles in "sample packs" from many vendors .
Thats all for now. Any more questions ,feel free to ask.