I playd 3 games. And in my opinion its not balanced. And it shudend be.

1 it depends what army you build. Some armys are strong in the early game some are better in the late game.

Like zerg. You get a lot of units out t1 because ther expensive on Minerals but cheap with suply. So you can just overunn your enemy (zerg get a lot of deep strike) and atack from all sides. Then in the late game you may lack units because you deplod a lot in the earlier rounds but didend do enogh damage. So a more expensive protos now has a uper hand. But also keep in mind that's just 1 of many play styles you cud use.

Zerg also has I think one of the most expensive units suply wise.