The seller of the keyboard should be suppling you either the needed screws or rivets or both depending on what you need for your given system. If they don't offer them look for a different seller.
You need the required fasteners and you do need to put in the correct ones. Apple has three different layouts screws only (A), mixed screws & rivets (B) and lastly rivets only (C).
While at first people used screws on either B or C setups to replace the rivets it was messy and the screw heads still could rub on the battery which is not too smart.
As time moved on plastic rivets became available! Today the keyboard suppliers offer the needed screws and/or rivets for the given keyboard.