Depending on your method of access (like app or webpage) often there is a way to browse without an account. Though you won’t be able to comment, vote, or save anything (like settings). So really, to sign up on a new instance, you pretty much need an account to do all this - otherwise abusers would send so much spam everywhere, this is why accounts are mandatory.

Although once you have an account on one instance, you automatically get to see content from all of them. Make sure you are looking at “All” rather than just “Local” content.

When you are ready to switch, go to account settings, scroll to the bottom and choose Export, then in the new place choose Import and it will port over all your subscriptions, block lists, etc.