I think you’ve pretty much nailed it. The trick is indeed to seperate your incoming data (eg. Octopus) right at the level of "Physical Input". Only data you want to record goes to the "to the Recording & Thru" object (and that’s the current selected track).
Recording your Octopus data is a little bit trickier because you use 2 different ports instead of 1, but it’s possible. If you need any help, let me know. Screenshots are handy in these situations.