I don’t use unregulated devices so none of these are mechs but all take replaceable batteries. you won’t really find internal batteries much once you hit that wattage level. I prefer removables because if your batteries crap out you only have to replace them if the internal batteries go the whole thing is trash. The batteries are not nearly as dangerous as the news tries to convince you. The removable batteries are entirely safe so long as you are constantly practicing batter safety(not keeping loose batteries in your pocket, not using damaged batteries, not using cheapo batteries etc. More here https://www.vaporesso.com/cloud-comm...battery-safety)