I don't have one, but I have three-- maybe 4-- of the RX200s. The 510 connector can give some people trouble, but I don't have any problems with mine. Any big-cloud tank will work on the silly thing; I suspect the '12 would be a good choice. You also don't have to open it all the way. I vape my 200s at about 40 watts. The batteries last for days
For batteries, my go-to cell is the LG HD2C. Be sure, when buying batteries, to deal with a reputable supplier. Counterfeits abound so be careful.