G'day Benedikt,
Although I believe TiddlyWiki is the cat's meow and then some, I think Notion is always worth looking at even if just to look at.
To me, Notion seems like the no fuss no muss quick way of setting something up IF you don't need all of the power and flexibility of TiddlyWiki.
All of that aside ...
I often tell folk: "to look at me, you may think the hamster is dead, but the wheels are always spinning."
I've various TiddlyWiki experiments on the go, one being a nodejs TiddlyWiki "Farm" on a server. The other is the idea of single-file TiddlyWiki instances acting as clients and/or servers (or peer-to-peer TiddlyWiki instances) all "talking" to each other with help from a web browser's local storage (all of those TiddlyWiki instances needing to be in the same physical place/domain.)
Mashups. Oh how I love them...
I'm thinking of playing this afternoon with humble beginnings of a single-file-instances TiddlyWiki "Farm" communication/sharing with each other via local storage.
Stay tuned. (Maybe I'll have something today, might take me a few days to demonstrate something in a YouTube video.)
(If this has been done by anybody already, please let us know so that I don't go reinventing the wheel ! Or inventing a rickety wheel when there's a muscle car out there ...)