It doesn't meet your requirements for small size or removable battery, but my iTaste MVP 3.0 Pro is absolutely amazing. It has a huge 4500 mAh internal battery, and Innokin uses good batteries that last -- my years-old MVP 2.0 still holds a charge just as long as it did when it was new. I have absolutely no worries that the battery will last for a couple of years minimum. It can charge your phone or other devices in an emergency and still have more than enough battery life to last the rest of the day It's built like a tank -- I just accidentally dropped it down a flight of stairs and into a solid oak door, and it didn't even leave a mark.
It's not a small device, but it isn't unmanageably huge; it's just a tiny bit bigger than my old MVP 2.0, and it comfortably fits in my pockets. Regarding power, 60 watts is more than enough for 99% of my vaping -- my "go-to builds" on my mechanical mods before I picked up the MVP 3.0 Pro was a 0.7 ohm single coil (2 mm diameter with 26 gauge Kanthal) and a 0.5 ohm single coil (2.5 mm diameter with 24 gauge Kanthal), for 25 watts and 35 watts respectively. And I only very rarely went below 0.3 ohms, which matches the 60 watt maximum output of the MVP. In those rare instances when I want to go above 60 watts, I still have my mechanical mods and 30+ amp batteries (Sony VTC4/VTC5 and purple Efests).
My only complaints are very much nit-picking. First, to "auto-scroll" when adjusting wattage, you need to press the + or - button once, and then press it again and hold. Second, when adjusting wattage, it will round-robin from 60 watts to 6 watts (or vice-versa) without pausing. And third, the screen, while very bright and readable, should have used a sans serif font instead of a serif font. And finally, while the coil resistance is always shown, the voltage it will use to reach the set wattage is only displayed while firing (it reads 0.0 volts when idle). All are really nothing other than (very) minor annoyances.
So even though it doesn't have a removable battery and is not the smallest 50+ watt mod on the market, I still think you should strongly consider it. At just $55, it is an absolute bargain for such a well-built and solid performing mod.
