I had this same problem with the Asus AC86U and am now experiencing it with the XR500. I thought that since the R1 handles everything so well in this regard I would have much better luck with the superior hardware on the XR500 with DumaOS blend - oh boy was I wrong. Same spikes, same problems.
How is this the case being that it's using essentially the same software to route everything? I have a Gigabit connection with 994 down/42 up.
Don't have a very sophisticated setup either I'm using an SB8200 Docsis 3.1 modem.
Have CC at 70% for both (have experimented with no luck).
Btw I see pingplotter being recommended as an alternative, but truly it's not. PingPlotter traffic is so minuscule that it's not subject to the same level of congestion that typical traffic would be. DSLReports bufferbloat test is indeed accurate unfortunately.