I would like to create a feed for visitors that shows Topic feed plus other stuff from Pages, Calendar, etc. instead of All Content which shows  Forum posts feed etc.

The current All Content feed adds every Forum post, which makes it difficult to read and clogs the feed backwards for my taste.

Am I missing something or it's not possible.

You can create that feed, but it needs to be a custom feed, not the All Content feed, which as the name already says, shows all content always. 

Thanks, you're right. It seems only when I complain about something I look hard enough for the answer...

I had made various feeds but none with the right options.