I believe the idea here is the audio should get priority, not ONLY trying to prevent bufferbloat more generally
I’ll quote @pcunite :
There seems to be some confusion here as to why we place different traffic flows into respective Queues. This need unfortunately prevents us from showing a simple configuration. This article is not merely about overall latency or even about overall bandwidth availability. Rather, it is about protecting high value traffic, knowing what that is, how to identify it, and then placing it within a protected scheme while still allowing decisions to be made about other types of traffic, under highly congested situations. You can not rely on a shaper or queue algorithm to figure everything out for you.
And recommend @pcunite’s tutorial: http://forum.mikrotik.com/t/using-routeros-to-qos-your-network-2020-edition/66683/1
In OPs case, only two sub queues are may be need:
queue-tree for “audio” & another for “everything else”
with a limit-at set for the “audio” queue, so it will get bandwidth over “everything else” if WAN queue is nearing max-limit.
But it the “limit-at” (e.g. “reserving” bandwidth in QoS) part that OP may be missing