I want to create a paid newsletter. Stripe works correctly with my Ghost installation.
Now, my question is: When I write a new blog post with “post access” set to “paid-members only”, and I enable the switch “Send by email” while publishing the post, will the email be sent to ALL members or to PAID members, only?
I am asking because I do not want that all members receive content that is reserved for paid members, only.
Emails are only sent to members which have permission to view the post - so yes, email respects post permissions 
It does indeed. But it is not clear that this will happen until you actually get to the send stage.
As a feature improvement I would recommend some clearer text and information be shown on views/screens BEFORE getting to the send stage to inform admin users of what will happen.
I was only able to work this out by doing test sends of each type of post.
Is there a way to find out who the emails have been sent to. For example, I have 3 subscribed/paid members - it is showing the post “Sent to 3 Members”… but is there a place I can see, which x members it was sent to?
The newsletter function is using Mailgun as an email provider. Mailgun has logs that show you who has gotten the email and who bounced it.
Would have been great to have it within Ghost as that is where the members are being handled. For instance, on the member’s page profile - a list view of which posts they’ve received.