Technically the character move component can be utilized to make most movement systems if you’re making custom movement modes, but I get what you mean if using it out of the box. The Chaos Vehicles system in Unreal is significantly heavier (and overkill) for RTS movements so that’s likely not the best course of action. The best alternative if you’re going to have that many actors is to create a custom actor that’s more lightweight that can handle the movement itself.
Also I’ve got some bad news on the massive unit count front, the baseline replication system is well suited for accurate and simple multiplayer replication, but would fall apart at Starcraft 2000 unit scales. It’s not guaranteed to be unplayable, but networking wise it’d be extremely infeasible, Raven goes over it pretty well on this post here:
It’s not impossible, and some developers have taken to writing their own deterministic lockstep networking to handle it, but it’s a big task to say the least. If you’re up to it, you’d likely also want to write a custom character controller as the baseline character controller is quite heavy in large quantities, if you want to go that route I’d start with stress testing very early to see just how much you will have to optimize to get to the scale you’d want.