If socialism isn't authoritarian, that means that people can opt out of social benefits, own their own property and things, and not have to pay taxes to cover others' social benefits, right? Without going to jail, right?

If not, then I guess we're talking about some form of authoritarianism.

To talk about "socialism" in a sense that doesn't break the non-aggression principle (necessary for non-authoritarianism), you need to think of volunteer communes. IOW, use pooled money (just think of it as a necessary evil) to buy 1,000 acres, build a master-planned community, and offer residency to people who pitched in to buy it, and then use socialism as the guiding ideology within that commune. If it doesn't work and people want to leave, they can leave.

That's a non-authoritarianism version of socialism. If you think there are others that exist in practice, I implore you to look into every true socialist country in history, including the currently failing state of Venezuela, wherefrom there is a mass exodus underway.