For a solo user on Windows seeking a modern file management experience, choose Files. Its WinUI 3 interface with tabs and dual panes offers features that File Explorer lacks, such as tags and column views. However, it’s only available on Windows and may have some rough edges in its preview builds. If you're strictly looking for a Windows-only file manager with an open-source development model, this is a strong choice.
On the other hand, if you need a versatile note-taking solution that allows you to manage personal knowledge and projects across multiple platforms, go for Obsidian. Its local storage ensures privacy, and the customizable nature with plugins makes it adaptable to your workflow. However, if team collaboration or cloud storage is crucial for you, Obsidian may not meet your needs.