Is it reserve seating ? or general seat we would like Seats together.

You can sit anywhere you like on the train. But it is best to reserve your seats/tickets in advance.

General

I've only been once purchased tix last minute and sat wherever we wanted

When we went it was sit wherever you like

General seats, but it's best to reserve your seats.

I believe large groups can reserve a section together.

When I did the train ride to the Christmas tree farm, it was essentially long benches so it's easy to sit with your group.