The main global feed is fine, I like the idea of an opt in tag that's just "Here's a random thing that I want to share with a random wider audience." I really don't see an issue with that.
As for the ones where it's global feed(topic) yeah, just do a topic tag instead. But the real solution is to say fuck it, care less, and throw as many tags as you want on your shit. If you post a gaming take, tag every form of the gaming tag you can, who gives a shit? Enjoy your lives, do what you want. Tag on whim and vibe, want more eyes on a thing, tag more things that are relevant, if you don't tag less, turns out, interacting with tags at all is optional. Go apeshit.