We used an airboat transporter up there last year and hunted from a camp on the Echooka River. I think the advice you have gotten thus far is very good. I would be cautious of any transporter that promises to “take you farther than the other guys” for more money. At the very least, I would get that promise in writing in your contract. There were other groups last year who said they were promised to be “X” miles from any other group and that proved to be untrue. The situation is complicated by the multiple airboat operators in the area - nothing prevents a different company from dropping their hunters right next to you.
I did not get the impression that the different companies talk to each other about where the caribou currently are. From what I experienced, it seems they use the same campsites year after year, and you just hope the migration comes near you (it never came through last season).
I’m also not sure how useful it is to set up a spike camp away from the river. Keep in mind many of those rivers are pretty winding, and there are hunting camps every mile in many areas. Last year there was a group that hiked 3.5 miles from their camp on the Echooka River and set up a spike camp. What they failed to realize was that with the curvature of the river, that hike put them 1 mile directly behind our camp on the river. They weren’t happy to see us hiking past each morning, and we weren’t super thrilled to have someone camped on the ridge right above us.
If you want, send me a message about which transporter you are considering. I have a feeling it is probably the same one we used because I saw they were offering a “special” spot for more money this year.