I think somewhere they said Sovereign, was a Scout for these So Called Reapers, and Scouts are usually smaller the the rest.

But, when I think ov The Reapers, I think ov the Machines in The Matrix, just more BA and Deadly

And they're probably Human sized Reapers. I just don't see how Massive Machines invading a tiny planet, Killing everything, without destroying the planet itself.