You may want to consider an RDA that provides the ability to run either dual hole or single hole in the event you want to only run one coil.
Or... one bigass hole, to feed singles or duals. ;-)
Read on.
There are a few unique designs, which are 3 post, but don't have the negative aspects associated with a 3 post used with a single coil, or a 2 post when attempting to fit duals. The one that comes immediately to mind, that has had sufficient popularity that there are several clones of it... is the
"Faceless" Veritas.
There are so many features to the Veritas, one that is completely unique and useful, that it's easier to point you towards a review of the original than to write it all down myself.
Although filled with the usual subjectivity, this is a good review, as it begins with the first original Veritas deliveries, through the assorted, first build opinions, and on to the current impressions after long term use. Again... there are
clones in just about any metal finish you might desire.
The only negative, that might impact you as a new dripper builder, would be that the Veritas is really designed as a vertical coil RDA... and some folks seem to have a hard time with verticals. You can build it with horizontal coil(s)... but the tails can end up slightly long when the coil(s) is positioned correctly in front of the air port.
From a personal perspective, having own(ed) over 40 drippers - originals and clones... along with the Origen and Magma, the Veritas is one of my favorites, and the only dripper I trust to not leak when out and about. YMMV