Hi Tom - please see PM with private video capture on resolving the issue.
For public benefit:
Issue was not at all caching related but to do with the custom access settings and custom user group as well as mistakenly thinking I need to set guest user group as the default instead of the registered group as the default.
Might be a good idea to expand a bit more on this topic in documentation.
Like, when and why to make another usergroup a default.
Maybe this is the reason the custom guest user groupI made was not working, as I had set it to default, thinking a visitor is the default situation, lol.