
As others wrote, blocking is okay. Using the timeline that follows only your subscriptions might work too (instead of the “all” timeline), but that would have the disadvantage that it is harder to find “new stuff” (unless it would be posted to the communities you are subscribed to).
I only know that this post was posted in the instance news community. From my understanding, the NSFW flagging is automatic now (no matter what). Although I guess it won’t hurt to check that box when posting. So it is a thing on the instance/server side and not on your browser’s.