I was looking for box mods similar to your requirements. I went with the ipv2s. 70w, single 18650, upgradable, USB charging, memory presets for wattage, all in a small package. I'm really happy with mine. Btw, the 2s box is different from the ipv2. All the seams are flush and the bevel on it is a nice touch. Replacing the screws in the door with magnets are a must. The stock allen screws are tiny and strip easy.