CB ... can't say anything about the seat mounts, no experience with any.
But, on the pole holder height question, I can suggest doing a little faux sizing before deciding. I've fished behind 18" & 24" pole holders ... and prefer the 18" height. I even sat in my boat & measured how high the bar could be, and still be a comfortable reach, before committing to buying my rod holders.
The 24" holders are not real bad, they're just a wee bit cumbersome to reach "over", in order to remove the rod on hookset ... unless you grab the handle (behind the reel) out of the cradle. At least that's what I've experienced when fishing with a buddy of mine, that has the 24" height holders (back seat). He even has 18" height holders up front, that he uses, and he spider rigs almost exclusively !!
On my boat, I have the 18" holders placed where they're within easy reach, with a little forward bending, and I can grab the rods by the handle (in the cradle) or in front of the reel. I'm fishing out of a 16' ProCraft, so I don't have as much open space as you do in your Ranger ... but, I use a offset pedestal seat pole, so I can move myself around to a comfortable position (in relation to the rod holders & the trolling motor foot pedal).
12" height rod holders might be a bit of a stretch to reach, but doing a measurement would show you the optimum height for your reach/bend distance. And there are rod holders that are "extendable" to varying heights, if the 18" or 24" heights are still a bit awkward for you.
... cp