Time for some more word of mouth (potentially): have you tried Beyond all Reason? It’s more or less a modern open source remake of Total Annihilation. Runs like a dream even with tens of AI players and tens of thousands of units in-game.

Compared to SupCom I would say there is more unit diversity but less wacky experimentals, and the commander unit cannot be upgraded. There are currently only 2 factions, that basically map to UEF and Cybran from SupCom (or rather SupCom derived those two from the 2 in Total Annihilation). The dev team is currently working on a third faction that, from the previews, seems to me to be a mashup of the Aeon and Seraphim from SupCom: Forged Alliance.