Well first off, congrats on making the decision
These little beauties are the greatest things since pockets in pants (which I believe Al Gore invented).
It looks like you've done some research, so I'll skip the basics other than to suggest that you consider picking up a couple of extra springs, maybe a rebuild kit (for just in case), and possibly a button cover.
As far as atties go, here's a quick reference guide to the physical dimensions of the various offerings Rob has on the reo site...
http://www.e-cigarette-forum.com/forum/reos-mods/601169-reomizer-physical-comparison-chart-rm2-rm3-rm4-rm5.html
Now, judging by the fact you've identified the Odin as something you'll like, the RM4, 5, and 6 are the most like it - larger chambers, built more for direct lung inhaling, dual coil builds work most "natively". You can dial the RM4 down to MTL inhaling in a pinch, but it's a natural lung'er, really.
The most popular atty is the RM2, and generally considered a staple in a good reonaut's arsenal. It's a smaller chamber, easiest to build with single coil, and regarded as the gold standard for flavour chasing. I personally like the RM3 (dual coil version) as I find it's like the RM2 x 2, with the same flavour-first tendencies.
There are other non-Reosmods atties to consider as well, and a good place to discuss those is in this
thread, hosted by a reonaut who
mods atties of all kinds for bottom feeding (which you need for use with the Reo)....
http://www.e-cigarette-forum.com/forum/modder-accessories-supplier-forum/581604-catfish-atty-mods.html
I hope some of this helps. Happy
vaping.