There are many experts on this forum and I am not one of them. Much as you are doing, I started with a new pond a couple of years ago and have learned A TON from this forum. The best thing you can do is to use the search function every time you have a question. All of the questions you present have been discussed many times before, which creates an incredible resource for new pond owners.

I think it is safe to say the first priority of all of us Pond Bosses is to create a natural, healthy aquatic environment. We like our fish, but we enjoy (maybe more) the vast array of plants, birds, insects, amphibians, etc. supported by a healthy pond.

Now some quick answers to your questions. Bluegill readily accept pellets although they may not want to compete with large cats. I'd think you'd want bluegill as a feeder fish for the bass and cats, and because thay are fun to catch and eat. Fountains help the water quality but not nearly as much as a aerator/diffuser. You'll have to decide how much a priority you place on the looks of a fountain. I personally see them as "unnatural" and wouldn't want one on my pond, but I admire their beauty in a more formal setting. Everything I've read says aerators really don't impact pond weeds/algae. Instead, they eliminate the layer of unoxygenated water that settles to the deepest part of your pond. This accelerates the decomposition of the "muck" layer that always forms on the bottom, and in effect expands the size of your pond because the fish can live at all depths.

Do a search for "aquashade." Some don't like the unnatural look while others think it adds beauty to the pond. It blocks light thereby reducing the amount of weeds that can take hold at the lower depths. However, some experts believe it has a negative impact on the frogs, crawdads and small invertebrates that are essential to the life cycle of the pond.

You can feed frequently, as long as all the pellets are consumed. You don't want a lot of uneaten food fertilizing the bottom. Most would advise against bringing in pike, or any other fish from another pond. You don't know what parasites or diseases they may bring with them. You are better off finding a fish farm with a good reputation. The key is in balancing the predator fish and forage fish. The catfish are fun to feed, but aggressive eaters who could ultimately take over the pond by eating all the smaller fish. If this becomes a problem you may need to harvest some of them and replace with smaller ones and/or add plenty of hiding places for the small fish. Search for "structure."

Hope this helps.