Well, I'm not supposed to troubleshoot here, but I'm done anyway......
I really really really reallly really really really really don't know why, but it appears as if the lack of a SSDT-USB.aml file was causing this problem. Thanks to
@pastrychef , who urged me to create one, I think adding one worked. Now on this motherboard, I've gone through a LOT of upgrades without a SSDT-USB.aml, and it's never been a problem before. But it looks like this time it was an issue. I was able to grab an aml template from
@ammulder's post and modify it enough to do some uia_excludes and that seemed to fix things.
Or maybe it was because I did the combo update, unplugged and offline - not really sure.
After the install of the most current Nvidia drivers, and the latest AppleALC, Nvidiagraphicsfixup, Lilu and VoodooHDA (I use it strictly for HDMI audio and it works great with AppleALC), Audio via HDMI works, the Aquantia 10GBE card works great with the patch provided by someone who shall not be named in this forum, PMHeart patch fixed USB3, so everything seems to be working.
No LAG, of course, but I use Firefox, and never really experienced any lag before, so I'd be surprised if I saw any.
Oh, and I am running Clover 4424.....and that seemed to help some too (if nothing else, it seems faster)