So are there any kind of safety concerns with a 150 watt mod? Not sure if I would ever vape close to that many but I can get it for practically the same price as the 60 watt IPV 2s
You still need to use safe batteries (good high drain IMRs with high amp ratings, like the Samsung 25R, LG HE2, or Sony VTC4), and when you're looking at a mod like the IPV3 that runs the batteries in serial, you need to be more careful with them. You should buy new batteries for the mod and mark them 1 & 2 with a marker or something. From the time you put these brand new batteries in until the time you take them to the recycling center, they stay together and you don't use them in anything else. Every time you take them off the charger and put them back in the mod, you should alternate which battery is in which position. The idea here is to make sure they wear over time as evenly as possible. If they're not balanced, you can put a lot of extra stress on them, which could lead to battery problems.
With a single battery mod, all you have to worry about is that you have the right battery. With 2 in serial, you need to make sure they match exactly.