Sorry if I came off as harsh with the 'hi-jacking' comment. I didn't mean to. That 70+ hours work week sounds insane. I'd be glad to see your test results once your work load lightens up!
I'd actually really like to see some more controlled experiments on what effect voluntary or full preemption does on the consistency of the latency on WiFi (especially with mwlwifi) with SQM under higher WAN (or LAN!) speeds. Then maybe another test on 100Hz v. 1000Hz tick rate (to see the tradeoffs between latency consistency v. throughput), and subsequently the combination of various preemption levels and tick rate. I am actually still not sure if this even applies anymore (or if it even applies to routers!):
...default Linux kernels are often compiled with HZ=250 (or even lower), causing burstyness and non-uniform delivery of packets; building your kernels at HZ=1000 will reduce this effect...
For now, there is historical data (but mostly conjecture) on the r7800 build thread by @hnyman and this thread. User @shm0 probably has more solid evidence than I do, and his/her data is much more relevant to us given that he/she owns a WRT1200AC (and I think he/she has also managed to overclock it to 1.6GHz - up from 1.33GHz!).