Most build their own coils for them, but you can get coils pre-made (the people at the shop will probably be happy to wrap some coils for you to find the build you like.) All you have to do is stuff them with cotton, wet your wicks, pulse fire and blow on em a couple of times, re-drip, and then you’re vapin! Coils can last a long time with proper cleaning, but cotton has to be changed every day or two.
Bit of a learning curve to maintaining them – coil building, is, in iself both an art and a science. But you could dabble with RDA’s on a KBOX. Most drippers tend to go for more power than that, but the beauty of them is that you can build a coil and set the airflow to make it work at whatever power you want. They allow you to tailor a vape to your whims and limitation.
As for RDA’s, there’s a gazillion of them out there. Look for ones with a deep juice well and the split-post center block (two outer posts each with one hole and then a center “T” post with two holes.)
The best advice I can give you is to go into the shop and have them set you up with a cheap RDA. They can give you the rundown on how it all works and how to make it work the way you want it to on your KBOX. They can probably set it all up for you if you just want to try it out.