For a networked game, on the technology side, make absolutely, positively, SURE that you split your simulation into the distributed/networked/authoritative simulation, and client-side “fixing upping” like particle systems, leg IK, etc.
In more detail: Unreal Engine isn’t great out-of-the-box for RTS games with lots of units, because RTS games generally use “deterministic simulation” to make sure that lots of units for lots of players can all be simulated without overflowing any one user’s internet connection. Unreal Engine uses variable (client-dependent) time steps for its physics engine, so you cannot re-use the Unreal Engine physics engine as-is. Also, Unreal uses PhysX for simulation, which is a library that is not guaranteed deterministic (even on the same machine – much less across machines.) Thus, you should plan on using some other simulation engine for the authoritative game state, and use the built-in physics only for client-side effects that don’t actually affect gameplay.
Other things that really matter for RTS-es, but are also good for other networked games, includes the ability to checkpoint all the game state at a particular time step, and restore it EXACTLY. You can then do this for all players at the same time step, and compare the checkpoints. If they are different, you have a de-sync bug. The ability to record all user commands and network inputs is also useful, because you can then play them back and make sure that the same game state results each time. (Also great for reproducing bugs, and automatically testing that bugs don’t regress.)
Here’s the canonical article on how to do networked RTS gaming. It’s written for the day of modems, but pretty much everything it says is still a concern for modern RTS games: http://www.gamasutra.com/view/feature/131503/1500_archers_on_a_288_network_.php
Read it. Understand it. Love it. Never forget the lessons it shares!
Note that, if you have never built a game before, or never worked in a software development team before, a networked game is not a good starting project. And, if you’ve never written a networked game before, a RTS game is not the easiest kind of networked game to start with (the only harder IMO would be a MMO.)