1" of fish per 5 gallon rule
This is really much more of a guideline then a rule. There are just too many variables that go into it. The type and amount of filtration, feeding routeen and fish selection (clean vs. messy eaters) will all play into this. Your fish list looks okay, provided you have the proper biological filtration to handle the bioload. remember to add the fish slowly so you do not overload the filtration capabilities of the tank. the question of "overstocking" is easily answered by turning to your water parameters. If all is well, you are not over stocking the tank. Keep in mind, there is a big difference between overstocking and choosing the appropriate fish for the appropriate tank. The fish you have choosen are appropriate for the tank.