I’m not using any particular organization strategy like Zettelkasten or PARA or anything. I am using Obsidian for most things, but my to-dos are in Apple Reminders and there are some scattered pieces of information in Google Docs and Notion that I still have yet to migrate to Obsidian.
Obsidian + I have a system where everything is an object and each object is a .md note. No folders. Objects can link to other objects as their type (THE_MATRIX_1999 links MOVIE as its type for example), objects can also be linked like this (related to XYZ, prequel to XYZ) or anything else really. I can create infinite virtual hierarchies this way. I also have a system that randomly reminds me/features certain notes/objects, on da daily basis - so I never forget about a note I may care about forever. I can also adjust how often I want each object to be featured to me from daily all the way up to infinitely rarely.