Firewall’s default action is accept. Imagine it as invisible “/ip firewall filter add chain= action=accept” at the end of each chain. I prefer to add unconditional drop/reject, like you did with input chain.
Order of rules is important only within same chain. Otherwise chains are independent on each other, it doesn’t matter if you have input before forward or forward before input. You can even mix rules from different chains together and it will still work the same (but it will be harder to read for you).