Welcome! Don't worry about the questions at all. I was once where you are at now and so has everyone else. Everyone in here is pretty nice and we'll all help you.
First of all, with your lighting, if your not going to have LIVE plants, it really won't matter as long as it will correctly fit the tank itself. Second, the filter will be moved to the back of the tank, instead of the side.
The heater should be about 3 watts per gallon roughly. 1 heater will suffice for your tank. Don't get one too big, or it will change the water temp too fast for your fish.
One thing about the fish, either one or two bigger fish, or lost of smaller fish. Make sure you save room for a pleco (algae eaters/ sucker fish) and 1 or 2 cories to eat the food left over on the bottom and stir up the gravel.
You can get 15 Neon Tetra
easily if you want. If you like the Neons, try the cardinal tetras. I favor them just a bit more.
Otherwise I wouldn't suggest many fish that get more than 4 inches long. I like the set up with 6-8 and a Red Tailed Shark
. The fins match pretty will and they will play around.
You could have a small piece of driftwood for the pleco since they have basically a vegetarian diet and make sure to get them algae discs (5 bucks for a few months worth) Feed once a day or two just before bed time.
The other fish will eat flake food, but also give them frozen bloodworms and chopped up earth worms from time to time. They need a variaty (too early to spell) of food also.
You should be able to shorten your filter by taking off the extention. The filter isn't too big. It filters 2.5x the size of the tank. My 55 gallon has has enough filtration for a 220 tank.
Sand and gravel is your choice. I would use gravel and go with a darker/natural color. The brighter your gravel is, takes away from the fishes colors.
I don't use bubbles in my tank, but I do have the water line low enough that the filters make a little of there own when coming out of the cartridge.
You will need to get atleast some AquaSafe tap water treatment and just read the directions.
I do suggest you fill your tank and let it run completely, minus the fishes for about 2 days, add about 6 Neon tetras and make sure they are okay for a few days and then add the algae eater and cory and if everything is still okay add the rest of the fish you wish.
You know about water changes, right? Add water once a week or so that has evaporated and once a month, change the carbon media in the filter and vacuum the gravel and do a 10% water change.