We took the short ferry both ways. Next time we might do the long one overnight and have a cabin for fun, but the price is much higher that route.
The ferry operation is very well organized, and they will email you if there's a delay on your reserved departure.
One tip since you do have turn off the propane on the ferry. Freeze ahead some baggies full of ice cubes (or blue plastic packs) and put them below. Kept everything in there cold.
We didn't bother reserving a seat or cabin on the short ferry, didn't miss it. Bring anything you need like meds because you can't return to the vehicle deck. There are TVs in the seating area. Food was reasonable and good in the restaurants. You can go outside for fresh air and the view leaving and arriving.
You can pick up a little wifi on the ferry, not great.
