A forum for woodwind musicians sounds like a great idea. I imagine there are some difficulties with being a wind musician with the current issues around covid.
For the problem you’re having with setting up Adsense, can you try following this guide to see if that solves the issue: Official Advertising / Ad Plugin for Discourse? The guide was recently updated. Let us know if you run into any problems with it.
You are correct that admin users can bypass a category’s tagging restrictions. If you’d like to get a sense of how your site works for non-admin users, try creating a second non-admin account for yourself and use that account for testing.
I’m going to move your topic to our #support category. I think it belongs there. If you don’t get an answer to your question about parent tags, I’ll have a look at it later today.