Ryan, parallel protected batteries, both in good condition can be connected in parallel and charged. The charger will apply a voltage to the batteries that will not allow one or two or three in parallel to be overcharged. The voltage will be the same to both parallel connected cells. Some chargers can not supply adequate current to two low batteries until they are almost fully charged. The little hockey puck chargers supply about 150ma. Two cells might need more than that until partially charged then the charger will apply a maximum of 4.20 volts (typical) and the battery will charge up to 4.20 volts, either or both of them, and then stop accepting current.
When you vape on the parallel pair you load them to maybe 3.80 volts, either or both. When you stop vaping the unloaded voltage will equalize between the two cells. There may be a small amount of charge that is transferred between the cells to equalize them since no two cells are exactly the same. When you get close to cutoff voltage, one will stop before the other and and the remaining cell might provide one or two more vapes before it cuts off.
There are several commercial Li-ion battery packs with 2, 3 or more cells in parallel and some with a single protection circuit (large enough to handle the rated current).
Do a search on Li-ion packs. Some might have 24 cells in parallel.
Series connection of cells is a different animal all together. Charging and discharging series connected cells does not inherently equalize the cells like a parallel connection does.
