Obsidian Note vs Tag
I use obsidian tags for marking note types and everything that can be related to Zettelkasten "flow" and notes lifecycle.
For tagging topics I use notes. It works smoothly thanks to Obsidian auto-renaming and autocomplete notes capabilities.
I tend to keep topic notes non-existent and only create them when I want to create an index note or a topic outline.
I don't mind creating a ton of non existent topic notes. Eventually, notes that have some related topics get connected on the graph.