I was in Neue Schwanstein last weekend. I got on the IC at the stop Frankfurt Airport at 00. The train was via Stuttgart around 2. I got off the train at Munich, where I took a train to Buchloe. From Buchloe there is a train to Fuessen at 9. After waiting for around 90 mins, I was permitted to enter the castle. When I came back from the castle, I found the square outside the Tickets-centre was full of the people. Horrible.
Therefore, I strongly suggest you should get there earlier, if you do not book the ticket online.
Therefore, I strongly suggest you should get there earlier, if you do not book the ticket online.