Hello... OP here, thanks for all the BQMs shared and the discussion.
I finally did my upgrade from SH2AC to Hub3 (both in modem mode) and M200 to M350. It went perfectly and my BQM looks exactly the same as before. I can't say for certain all traces of the Puma 6 issues have been mitigated, but as I may have mentioned in my first post, five years ago with Hub3 on M200 (or whatever it was at the time) my BQM was always full of yellow spikey latency, and that certainly is not happening now.
https://www.thinkbroadband.com/broadband/monitoring/...
(the red is when I did the switch)
Interesting but not surprising: single stream download speed did not improve too much. With old set up it would be close to 200Mbps on a good run but could be in the low 100s also. On the 350 service single stream is more consistently around 200Mbps and multi-stream hits 370Mbps. I'm pleased my upload also improved from about 21Mbps to about 32Mbps. (I have a little traffic shaping running on my opnsense router)
https://www.thinkbroadband.com/_assets/speedtest/but...
My Puma6 test at dslreports.com does show a few latency outliers, but my connection isn't totally quiet so I'm not too concerned with it.
http://www.dslreports.com/tools/puma6
(server 56)
59ms : x
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78ms : x
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82ms : x
100 - 149ms :xx