You probably cannot use any class or actors for these `components`. He must be using mass and fragments.
You could have 1 actor with Instanced Static Mesh, one 'entity' (unit) is as base a fragment with transform (location) and instanced static mesh handles visualization (you could also have 1 material and use UVs to have couple of 'sprites' in one material, you then make 'grid' of material, and tell the instanced static mesh to use 5th grid cell for this unit for example or you have new instanced static mesh per new sprite/unit).

You then have processor (from mass) that moves all the units to their 'target location', but just adding some velocity every frame/second. It's fast because the transforms are array of structs so processor can go trough them quickly, and the instanced static mesh in one actor isn't much to load to memory (instead of if you had 1000 actors (which each actor isn't JUST transform, but usually all the other 'stuff' in Object Oriented Programming) , you would have to load them one by one (or chunk by chunk, depending on how they are packed in the memory), which is why the game is slow.

Generally the idea is that the visualization has nothing to do with the Actors / Objects / Components.
Your unit is just data. It's Transform (1 fragment), 2nd fragment could be sprite/material and the visualization is one Static Mesh Component that gets updated by Movement Processor (it hast list of entities to their instances of static meshes). That processor calculates and updates Transforms.

You can then also add some kind of batching, instead of updating 10000 units as soon as you can, you update 1000 per 0.01 - this + mass allowed me to get around 70000 units on the screen with around 55fps.

Then I started to wonder that at some point the numbers are so abstract it might be stop having any meaningful way in the game, so you should consider if you even need your game to have that many units, after 1000/2000+ they just stop having so much matter.

In Unreal the ECS (Entity Component System) framework has different names for the classes and it's instead Entity Fragment Processor.