Which Multiplayer System should I use for a battle royale game development?

Photon Bolt is going to be the best for a shooter/FPS, you can have full server authority (for anticheat) or server enforced client movement and it already has built in interpolation/lag compensation, hitboxes, etc. Photon Bolt was built for shooters and also attempts to provide direct peer to peer connections using STUN/NAT traversal.

Photon Bolt also has a programmer-centric framework using generic types and other things that make it easy to use if you are a real C# programmer and not just a script kiddie.

Mirror and other packages won't provide the proxy/relay service and won't attempt direct peer to peer connections using STUN, but if you only want to have dedicated servers that may not be as important and other packages may suffice. Still, Photon Bolt has a nicer development environment.

Mirror's great but I can't get it to work well for mobile for some reason. You really don't need to do much scripting except for maybe coding how your custom UI functions from the scripts.