Your local fish store likely has fritz turbostart bacteria. It will help a lot with keeping the ammonia down and from killing your fish. Gives your tank a headstart.
So what happens with a new tank is as follows and is called the nitrogen cycle, do some research on it. Your tank is starting with no bacteria to breakdown fish waste into less toxic nitrate. So your fish produce waste, food rots, etc. This turns into ammonia. Bacteria eat this ammonia and poop out nitrite, then a different bacteria will eat the nitrite and poop out less toxic nitrate. It takes about 2 months give or take for these bacteria to build up in numbers enough for a fish or 2. Without the bacteria the ammonia builds up and kills your fish. The turbostart will dramatically reduce that 2 month wait because it is seeding the bacteria in your tank to start. You actually might be able to add fish a week after adding the turbostart, but it is wise to still wait longer.
Either way, before you add fish, add small amounts of fish food to your system. This will add ammonia to your water for the bacteria to eat. Buy a sechem ammonia badge and stick it in your tank. This will let you monitor your ammonia level without having to test.
Have seachem prime on hand before you buy fish. This will temporarily neutralize the ammonia if you notice there is ammonia in the water so it doesn’t kill your fish. Keep the ammonia badge in the water when you add fish so you can see if the water is being poisoned, this will allow you to act possibly before your fish die.
And to answer one of your other questions, everything on the list you decided on will eat frozen food.