You are absolutely on the right path!
I am not sure exactly how the dripbox functions. It seems to be a set 60 watt output. This means it varies the voltage to the coil based on the resistance. So even though it is not variable wattage, it is controlled by the chipset to keep you safe. The Pico and 40TC are regulated and very safe mods.
The batteries are good. They are not the longest lasting batteries, but very good batteries just the same. They will handle safely everything your mods can throw at them.
I personally have quit buying batteries from amazon. I have had good luck with them, but prefer going to a source that I can go back to if I have a problem, and also verify authenticity. My current favorite batteries/vendors are:
Samsung 30Q:
Samsung INR18650-30Q Battery 15A 3000mAh (Liion Wholesale)
18650 Samsung 3000mAh INR18650-30Q (Illum)
LG HG2:
LG HG2 18650 Battery Genuine & Tested - 20A 3000mAh (Liion Wholesale)
18650 LG 18650HG2 3000mAh (Illum)
You can also can catch them on sale at 101 vape and a few others for a great price.
There are other batteries that are coming out that look pretty good, such as the new Sony VTC 5A.