And how many of those accounts are for NSFW content?
For the sake of anonymity, people without separate accounts can pretend to be sock-puppets of those answering.
1 main and 1 nsfw just like I did on reddit
This is the way.
Though, my Lemmy illiteracy has lead me to make an account per instance. So I have one here, .world and nsfw. Is it possible to go on different instances with the same account?
Yes. You can use the search function for that, just search for “community@instance”, so for example “worldnews@lemmy.world”.
Linking to communities from other instances works similarly, using a “!”: !worldnews@lemmy.world
You can also append this type of address to your instance url like so:
https://lemmy.ml/c/worldnews@lemmy.world
As long as another instance is not explicitly defederated (blocked) from yours, you can visit any community from any instance this way.