True, but not relevant (a common misconception). The issue here is speed, not range:
Higher power can enable higher speed for the big download packets.
Response packets are not affected, but that doesn't matter, since they are tiny.
So while higher router transmit power may not increase range...
I'm a fan of the RT-86U, but I doubt you would see much improvement over the RT-AC68U. To improve your coverage, you might want to add either one as a 2nd wireless router using AiMesh.
From your list my recommendation is the RT-AC86U. It's the wireless router I deploy for high-end business clients where rock solid performance is the top priority.
A good alternative at less cost is the RT-AC68U. Most home and small business users would be hard pressed to tell the difference...