Ali
It depends on whether you want to use Auto-RP or not.
If you don't and you just want to statically configure the RP address on all multicast routers then yes you are correct you do not need the "ip pim send-rp-announce int scope 16" command.
As for "no ip pim dm-fallback" this stops the router falling back to dense mode if there is no RP for a group. So if your RP that you statically configure is responsible for all groups you'll be fine.
Jon