How to mirror 2 Ghost sites?

I have 2 ghost sites, but I want to mirror the posts and members or everything if that’s easier.
So when 1 site creates a post the other should post it too with the according uploaded pictures.
Now when a member gets created on site A, site B should create the member too, but also when a member gets created on site B it should be created on site A.

Is there a fairly easy way to do this? If so please let me know!

What’s the use case, exactly? Are the sites the same? What’s different about them?

It sounds like this almost needs to be one single ghost install, branded two different ways.

I’m simply making 2 sites. One has a sci fi story to it and is much less performant, because of special effects.
The other one is going to be a clean performant site which is going to be the main site.

So unless they have to be on different domains, I’d be inclined to handle this with theme files. You can have your ‘clean’ homepage at https://yourdomain.tld, but also have the special effects homepage that lives at https://yourdomain.tld/snazzy . Collections are not exclusive, so your routes.yaml could set up access to posts in both ‘snazzy’ and ‘clean’ formats.

Yes the problem is that it would be difficult to try and separate all the files to be loaded, cause I want to be able to optimize the load times.