From the Reo menu I think your best choice based on your wish list would be the RM3. (Guys, help me out there if I'm wrong about that. Papa would know...)
The RM3 or RM4 would seem to be your best bet of Rob's stable of atties.
The RM4 has afc, the RM3 does not. Both let you make dual setups (you need to get the dual version of the RM3 for that).
The deciding factors between the two are:
a) how airy do you like your draw? The RM4 is quite airy, the RM3 not so much (although you can ream the air holes to aid in that, if you so wanted). This means that the RM4, wide open, will get you bigger clouds. Some people claim they can dial the RM4 air flow down low enough to approximate the draw of the RM3 or RM2, but you're kind of fighting against the thing's nature.
b) how do you like to draw? If you're a direct lung inhaler, go with the RM4. If you prefer mouth to lung, the RM3 is a better choice (again, with the stock air holes).
c) how important is flavour? Small chamber atties get you flavour in abundance. The RM3 wins in that category (not that the RM4 is weak there).
Sooooooo... we all want good vapor and great flavour. Both these atties get you into that space, but you need to look into your heart - would you take vapor over flavour or flavour over vapor (given an acceptable level of the lesser variable)? If the former, it'd be the RM4; if the latter, the RM3 is your honeypot.
Myself, I'm a flavour guy who mouth-lung inhales - the RM3 (running duals) is my preference. Take this for what it is - one man's opinion.