When I poke around/research, I start wherever, then spawn "child pages" into the new tabs. But I have a limited capacity for dealing with the holistic flow after about seven tabs or so, especially because half way through I start with a new "top node page".
I'm not so worried about every last pixel of vertical space - so it would be an amusing addon that you can have multiple rows of tabs so if your have say five main topics going on, each topic gets its own line and then you intuitively know all the spawned tabs belong to that top node. (Maybe a couple misc junk lines you don't care about at the bottom.)
The best I can do so far is use my desktop splitter, then multi browser tabs, x tabs per browser, and the browser windows are color coded because FF main is orange and Palemoon is blue.
But multi tab rows would be neat.