Berth details for Tomakomai-Akita ferry

I've just started planning my next Japan trip, and looking at the Tomakomai to Akita ferry for one leg of it, and I was hoping someone on here might be able to provide some additional details of the different accommodation options. Specifically, I'm after a two person private berth, preferably with washroom. While https://www.snf.jp/english/pdf/Tsuruga_Niigata_Akita_Tomakomai-higashi... gives some details, in some cases there's not a lot of obvious differences. What I'm currently looking at is the State Room B, in either the Twin or Japanese Style version. From that page, it looks as though they should be the same price, but attempting to book via directferries.com has the Japanese Style one about 50% more expensive. I've tried booking directly through https://www.snf.jp/english.html, but not getting very far there.
Really hoping someone has had direct experience with this particular ferry and can help me out!

I've taken the Yuukari into Niigata, but I took Tourist J and camped out on the floor with only a few Japanese. You got a blanket and a plastic pillow, but there were so few people that we used a couple of blankets for bedding and one for covering. Most of the rooms were empty. I wandered through some of the bunk rooms and looked into some of the top floor rooms just to see what was there and none that I saw were even occupied.

It seems you're wondering about the Japanese/Western/Twin room differences. The Japanese style has tatami mats and you sleep on futon. You can get 3 people on the floor if the futons are touching side by side. The twin has two beds, one on each side, and the bunk room has a bunk bed on either side with 70 cm between them. In most hotels, tatami rooms are more expensive than "western."

The "Grand Bath" was an experience since we were going through some wave action which transferred to the bath water. Waves in the bath were rolling back and forth sloshing over the sides as you floated up and down and looked out the window.

The restaurant was a buffet style, and I found paying and hitting it up once was enough to last for the trip.

If you don't get reservations, you should probably be OK just showing up and purchasing tickets the day of departure. There's always a bit of risk in case a school group is traveling by ferry. However, this is a big ferry and there's lots of room.