Bare with me. I wrote this all below, and then almost just deleted it because I'm really confused now, and most likely I'm going to be slammed for not understanding basic concepts, but I'm posting anyways:
This just sounds so much like you're talking about a parallel setup, where the number of batteries influences how many amps are being drawn from each battery. Maybe the total output voltage is what's confusing me. I thought that a regulated mod, regulates, and it doesn't matter if the battery(s) are nearly dead at 3.4v or fully charged at 4.2v, it will regulate and pull the same amperage on the batteries all depending on what you have the wattage set to. Is that totally wrong to think that? For example, in your example of the 2 batteries at 3.4v each, lets take 3 batteries in an RX200 fully charged that's 12.6v, and with the equation at 200w, it comes out to 15.87amps per cell being drawn. Now as the batteries die, you guys are saying that amp draw on the batteries will increase if you still have the regulated box set at 200w. I thought that goes against what the regulate box mod. I didn't think they worked that way. I thought that the important voltage here was what the voltage/wattage was set to, and not the voltage that determines how much life is left in the battery. Is this because the RX200 although regulated, it is in series? I thought that they consistently pull the same amps on the batteries, depending on what you have the wattage set to, and they pull that all through the life of each battery's charge. So from 4.2v down to whatever it technically "dies" at, around 3.4v. I thought that's what the purpose of the board, or chip was.
When I'm calculating if a particular build will be safe to use in either a dual or triple 18650 regulated box mod, do I need to be using the sum of all the batteries voltage? In other words, to calculate my amp draw on each of the 3 batteries from a fresh charge, fill in 12.6 volts and the resistance of my build, to let the current and power values calculate accordingly? A lot of questions I know. Look at my logic, and please let me know if I need to research a specific topic to safely know what I am doing. I appreciate any more time you can take. Thank you.