OK, looking back at this again. Have taken some speed and load info from my box running 17.01.4, and the other C7 running 18.06.1.
I'm not seeing many processes running at 1%, at least somewhat after the first bootup. My bad on seeing a new column in top (?) VSZ% and thinking it CPU.
The 18.06.1 C7 does seem busier than the 17.01.4 one.
Seeing a bit less of the slowdown in Luci operations than the last time, but still noticeably slower in things like the realtime graphs, or any other page that has a lot of data to gather and display.
The networking slowdown is still there, I did test runs with ethernet and the 5Ghz AC WiFi, on both firmware versions and no SQM, Results below:
17.01.4 C7 v3 router
Router - ethernet - PC 250-270mbit DL, speeding up to 340mbit, UL typical odd 20's to 40's, with typical for my cable huge latency spikes
Router workload: ksoftirqd 40-60% CPU idle 5-30% (mid teens to 35% when below 300mbit, single digits when hitting 320-340mbit)
Router - 5ghz Wifi - PC 180-240mbit, avg 220's, similar UL speeds
Router workload: ksoftirqd 60-70% CPU idle 5-15%
18.06.1 C7 v2 router
Router - ethernet - PC 130-240mbit, avg 150's, a few moments peak 280, not 340's
Router workload: idle 5-40's%
Router - 5ghz Wifi - PC 130-170mbit, avg 150's, similar UL speeds
Router workload: ksoftirqd 40-80% CPU idle mostly hard 0%, occasional rise to 5%, sirq98%
As you see from the above, there seems to be a significant drop in speeds, with an increase in the loading of the system, though not entirely a clear cut one. A large drop in eth speed, but the idle time isn't hitting 0%, while you see a similar drop in the wifi speed, and idle hitting 0% for much of the time.
Later down the weekend, I will try to cross check between my two boxes, though I'm fairly certain that the difference between the C7 v2 and v3 (US one, not the Asian market one) is only in the wireless outboard radio and antennas, not in the processor. I might try 17.04.5 as well.
I'm wondering if there's a better system level tool or logger than top, to better capture what's eating the resources?