I actually got it all sorted (in my other thread... just too brainfried to fully update here with steps) BUT the impression I am getting is that when other people make these vids they don't use ASIO. So that allows two hardware devices to run at the same time.
Like all the vids I see talk about having the soundcard dealing with the system/game/program sounds and then they have a USB mic or external soundcard for the voiceover.
With WDM or MME that seems to be okay. Obviously I want to use ASIO for Sonar because it turns into a pile of poop otherwise (but with Win10 that may have changed with the audio improvements... I am of course still on 7 and all my projects are in ASIO and switching driver modes just broke EVERYTHING).
What Mirillis seems to be expecting is two interfaces. It doesn't expose individual ins/outs for hardware or virtual i/o. All it shows is the device and I guess just snags the first output. So a soundcard and a USB mic could be selected seperately in the two options (for mic and sys sounds). Running through the same device, even with Voicemeeter, just doeasn't work and everything gets jammed into one track no matter what.
The solution I've cooked up is to simply record the "composite" outputs from Voicemeeter into Reaper. VM with Composite enabled on the virtual output bus outputs the hardware inputs (VM 1 and 2) and the Virtual Input on their own stereo channels AND another stereo channel that outputs everything as usual.
In Reaper I just set up a couple of tracks to accept the feeds from the mic bus and the virtual bus and bingo bango... I get the system sounds separate from the mic sound. I could also set up another two tracks and snag the MAIN bus (with everything) and the other hardware input channel (which I am not currently using but I could do something like hook a guitar up to it through my Scarlett or something).
In Mirillis Action! I just let it record the first Voicemeeter bus (the main that crams everything together). I can use that as kind of a "bed track" to line up the tracks from Reaper to when I get to the editing stage.
Really wacky stuff but it's workin'.
Tenacity indeed.
lulzity!!!
Cheers, dude.
PS: The reason I went with Mirillis Action! is because it apparently has the lowest resource consumption with the best screencast quality. It's only $30 too.
Everything else (including Hypercam which is what Craig said he uses) has something or other wrong with it (Hypercam is now apparently a malware farm... ugh). None support ASIO (or so I've been gleaning).
The BEST of the best though and the one the Baker's apparently use is Camtasia... but that's $300 so that's out of my price range. It however also does editing and a bunch of other crap. Might even support ASIO.