So I've been playing around with the codel target today and it became clear to me that at least in my situation (high rates, low number of active clients) it really only has an effect with multiple stations generating load, and even then, it's pretty subtle.
If it's just one station generating load it's really only hitting the AQL limit and codel won't drop anything. If you add more stations I see codel starts dropping, but even then it seems that AQL does most of the work keeping latency down. It seems that codel only works on the packets that make it through AQL. Fortunately AQL on it's own seems to do a good job.
Anyway, for me changing the AQL TX queue limit makes a far bigger difference in latency under load.