I thought it would be a bit of both - communities are moderated, but instance admins have a final say in what (and how) communities are moderated. So you would need to ensure that that instance you choose has administrators that effectively allow communities to run with the “speech” you are after.

That said, I would assume any instance that allows “free speech” would quickly fill with hate and racism (and all the other things that people throw under the banner of free speech) and would be defederated quickly - which is a good thing!