Basically none. Both are mainstream instances, not practicing any extreme moderation policy.

You might have confused lemmy.world with lemmy.ml which does have some communities with bad reputation.

There’s a huge difference between a tankie and a socialist:

• Socialist supports economic policy aimed at just distribution of resources
• Tankie supports fascist-like authoritarianism under a mask of socialism

You don’t have to.

Anything really. No matter what your friends say, what your family says, you’re not obligated to live your life in a way which is not comfortable for you. Or put yourself into situations you dislike just to please other’s expectations.

Do it your way. Do your best to be a good person of course (according to whichever moral standard you hold). But do it your way.