Nice little video there... Not as in depth as I personally would like but it'll help a few persons I'm sure....
So I discovered ( well, told via Paul in my support ticket) the KEY to getting this to work just right every time with the MacBook pro. I'm posting in case somebody else finds this useful info that the Manual doesn't mention.
Start MacBook
Plug in usb end 1st, then into back of Stomp.
Then Start Amplitube.
That is all I had to do.. ALL settings were already configured as in
Ryan_IK message above.
In the past I had a ProTools rig running using this Mac. This might have caused issues that in turn had me trying to get the sound output to work. One of my config attempts I tried to use the old PT choice that is still in the sound preferences/settings. I think that's what sank the ship and caused all my issues for the rest of the night. Doh!
I Also updated the MacOS to High Sierra 10.13.4 to make sure that all needed audio information would be freshened and present on the Mac.
Everything else worked well from that point on.
***Total lag time from guitar > Stomp I/O >
Mac > Amplitube (two pedal configs,two amps, two inserts,two cabs different rooms with duo mics each, two racks, L/R output) > back to stomp > L/R outs > Focusrite > Reaper Stereo Input > Input FX (SSL E Channel, Softube Tape) > Monitor In > Focusrite Monitor L/R out & Headphone Out
-->Less than 1.6ms round trip, so that's a .8ms one way trip fingers to moving air with the Monitors - while monitoring a seperate 18(?) tracks of other inputs running simultaneously to headphone/mon mix.
Just sayin...
Rest assured I WILL continue to do everything in my power to push the limits, and hope to find none.