feed them both but make sure you dont over feed them. i would also buy two cory cats or a rubber nose placo or buy them both to keep your tank clean and to eat any left over fish food. and for your other question it will sometimes take fish a few days to get use to your tank

Fish are stress when you catch them and then put them in new water especially if the water is not the same as the water that they were in. If they do not eat the food with in a few minutes then siphon it out so that it does not cause problems by rotting in the tank. And they can go for several days without eating so don’t worry too much about that. The tank is going to have to “cycle” that is the fish are giving off ammonia which is dangerous to fish. But there will be a bacteria (that live in the tank) that will break down the ammonia to nitrite (which is also dangerous to fish). Along comes another type of bacteria that eats the nitrite and turns it into nitrate which is not too dangerous to fish. You need to keep check on the ammonia and nitrite so that you will know when the tank is fully “cycled”. You can take water from the tank (in a clean glass container) to the pet shop to have them check the ammonia, nitrite and nitrate along with the pH of your tank water.

You should feed them tropical flakes and yes they do tend to not eat for a couple days after you get them

They might like the flakes better but the pellets are better for the tank and the fish. So go with the pellets.

Also, due to stress of a new environment, fish tend to stop eating. Give it a few days.