I think this is a pretty good review of he RT-AC86U. It is long, but has I think some very useful comparisons towards the end, including some comparisons with the RT-AC68U.
I am in the US and was on the phone with Asus support a few days ago. I had some problems using my RT-AC68U with the CenturyLink Actiontec modem/router in bridge mode. I asked about a replacement for the Actiontec and the DSL-AC68U was the reply. I was assured that they would work together in...