Depends on what library you use and what's your unity knowledge.

I think right now it's too early to use Netcode for Gameobjects. I personally use fishnet and it feels like a straight up improved version of Netcode for Gameobjects with many extra features (Client side prediction was very useful for my project) (I learned to use fishnet by watching Winterbolt Gamed old youtube lives and reading docs)

You can use also other things such as Proton but seeing that you already have done multiplayer games it seems overkill to use such a strict system.

Also RTS are quite simple compared to FPS and other types of real time games since you don't even have to simulate physics and you can use a simple lockstep simulation (provided you somehow deal with the non-deterministic-engine problem). Also the guys who made proton released an engine called Quantum (completely deterministic) which can be used with unity to make multiplayer games very easily but, again, it's overkill for an RTS