You can use any rda you want, just have to build 1 ohm and above.
Fit / size wise I used the Atomic 18mm, and it was the perfect size/match for me.
The Atomic is made for single or duel coil/airflow control, but it is tiny to build on.
Gives great flavor(small chamber and all that) but holds next to nothing as for as juice well.
Good luck, anything will work , just might be top heavy looking and feeling if you go with a 22mm rda.