Hi, you have quite a few questions and issues all rolled into one there, so I'll try and help with some of them
Generally speaking, sinking foods are better than floating ones for lots of reasons.
Sinking foods help to discourage surface feeding and the possible intake of excessive amounts of air from the surface, this helps to reduce swimbladder and related problems.
Sinking foods like pellets are also good because they are extra compacted to help to remove any residue air in the pellet. The good quality ones also soften quickly and sink at a steady pace allowing the goldies to middle and bottom feed.
Hikari Oranda Gold are floating pellets, not sinking ones so they are designed to be eaten from the surface.
Surface feeding can be OK for some goldfish, but as we all know, fancy goldfish are more prone to swimbladder and constipation problems because of their body shapes and feeding from the surface can involve a lot of air intake as well as from the food.
Personally, I recommend sinking pellets with goldies but you can get over the problem by pre-soaking your floating pellets in a little tank water before feeding.
This enables the pellets to soften and become easier to eat, but most importantly it helps remove the residual air put into them in order to make them float and thus they sink. This also helps to discourage surface feeding and associated problems.
Some fancy goldfish are just more prone to swimbladder problems than others, such as the distinctive "golfball" shape of pearlscales for example and it also has a lot to do with the fishes genetics and breeding and as well as environmental factors. Prolonged exposure to poor water quality, like high nitrAte levels can be a cause I believe.
You can help prevent swimbladder problems through an appropriate diet and through maintaining really good water quality, like keeping nitrAte levels to a minimum as many members will tell you that their fish become more "floaty" when their nitrAtes go beyond a certain level.
Managing the diet involves discouraging surface feeding, pre-soaking food, feeding a varied diet and preventing constipation (which is the main factor affecting the swimbladder and causing fish to become floaty).
Some people feed peas on a regular basis, as a dietry supplement to help keep things moving and to prevent constipation and swimbladder problems occuring.
If your fish are floating now, the usual advice is to starve them for a 2-3 days then feed nothing but a pea for a few days.
When you come back to feeding them again, ensure you pre-soak the food and add variety to the diet like fresh veggies (there is load of info on those on this forum), add other dietry supplements like "live food" such as bloodworms, brine shrimps and daphnia (the latter has a slight laxative affect on fish too) - make sure you even pre-soak feeze dried foods if your fish are floaty.
Spirulina algea flakes are a good way of introducing more vegetation into the diet and also help to prevent constipation, I have found them to have the same affect as peas on my fish.
The key is to keep the swimbladder functioning normally in all affected fish, diet and water quality being the main factors. Also, be wary not to overfeed.
You also need to try and change your fishes behaviour in order to discourage and prevent them from surface feeding, they will quickly learn that the food you feed will sink below the water surface. Keep perservering.
In the meantime keep the water quality as good as it can be, paying particular attention to your nitrAte levels.
Sorry for the ramble, hope this helps a bit. I'm sure other members will have some more ideas