I have done the regular FW terrace dessert party and the Garden dessert
MNSSHP.
The view from the terrace in my opinion is not good, even if you are by the railing. If you are not by the railing, your view still is even worse, and you need to jockey for a better position. The FW are off center, you can't see all of the castle projections, and sometimes the ceiling blocks the FW depending on your spot.
The view from the garden is perfect. Well, it can be perfect. The best spots are all the way in the garden, so you are centered -- that's left side of the garden as you face the castle. The walkway in front of the garden on the left side is reserved for wheelchairs/scooters who attend the dessert party -- the CMs do not allow kids on adults shoulders in this area. The right side of the garden - -the walkway in front of it is open seating and there will be shoulder kids, so don't sit in that area. (Just to be clear, I am talking about the garden that is on the right side as you face the castle --- the left side of this garden is the better seating than the right side of this garden. I don't know what goes on in the other garden)
No, you don't have to enter the dessert party 60 minutes before. You can arrive later. It depends on how much time you want to devote to snacking. Personally, I don't really care about the snacks, I just want the FW spot. So we spent maybe 15 minutes snacking.
Last week on Tuesday and Friday, the garden area was 1/2 full at best. Probably less. On Friday we checked in around 855pm, had a quick glass of wine and snack, and then went back to the hub to watch the parade. We didn't go into the viewing area until around 945, but people were still entering as the FW were starting.
On Tuesday, everybody in the garden area stood for FW at the direction of the CM. They were mostly seated while waiting. On Friday, most people remained seated to watch the FW as the CM didn't come over and tell everyone to stand.