Much of our planning is complete but will use this thread for questions re specific details.

Part of our route will involve dropping off our rental car and taking the ferry from Frederikshavn Denmark to Göteborg Sweden.

An option is offered for reserving seats, in either a public area or with lounge access. Both are an additional $16 or so. Is this worth it?

I am just getting started on planning a very similar trip! Would you mind sharing your itinerary?

Note that the OP posted this over a year ago and has not come back. You would have better luck getting input if you start your own new thread.