Hello there. I’ve written about this a bit more here, but if you already have birectional linking set up between the apps you’ve discovered most of the secret sauce.
As to
why I don’t just do everything within DEVONthink
I just find Obsidian a more pleasant writing experience (WYSIWYG editor suits me better), and quicker to work with linking notes. I love how Obsidian treats [[future links]] as ghosts that can be linked to from elsewhere in the app even if the file in question doesn’t yet exist. In fact Scrivener used to be my long form writing app, and I am currently between that and Obsidian where I tend to draft more and more.
In Obsidian a few plugins also allow me to manage writing projects (outlining, canvas, Kanban, and so on), and it’s unparallelled for that. Obsidian is the more powerful markdown editor by far, and I really like it’s capacity to save custom Workspaces for each project (DT offer this too).
DT is a resource management app for me that allows writing activities, and I do do some writing in it from time to time, but it isn’t optimised as a writing tool. Obsidian for me is a writing environment that also offers resource storage (but it isn’t optimised for that so I don’t use it for e.g. PDF storage at all - because DT is infinitely better at it). So I use the best tool for each job suiting my particular preferences and circumstances.
I could easily take @MsLogica 's path, and occasionally think I should move everything across to DT. But I’ve crafted myself a very nice thinking space in Obsidian now, and would lose functionality that I enjoy and that helps me focus. Maybe I could recreate that in DT – but I am happy where I am between both apps.
If you like simplicity, stick everything in DT. If you like tinkering; crafting your bespoke writing/note-taking environment, keep trying Obsidian.