It is a little surprising to see a handful of recommendation for OneNote. I have never used OneNote before, but will definitely give it a try.
I think one's idea tracking system should cover two parts: fast and slow. The slow part is as you mentioned we should periodically review ideas. For this part, I am almost 100% happy with Github issues/wiki/projects.
For the fast part, like you, I used notebook, IM, Google Keep and a bash script at the same time (whichever that is most handy). I am 90% happy with the process. Given the high frequency of the day I am spending tracking ideas (~10 times per day), I am willing to spend some time to fine tune the practice until I am 99% happy.
The idea I have in mind is to write a IM-like note taking app for iPhone and Mac, which stores plain-text and image in iCloud drive. The app should utilize platform features such as Siri, 3D touch, Mac status bar to enable fastest idea capturing.
This sounds boring to me, but I believe if it is done right, it could be my most efficient zero-effort idea tracking solution on the go. (And review ideas using the plain-text db in iCloud)