[quotename BlueFalcon]The hardest AI is Expansion Insane Terran/Zerg/Toss.[/quote]
Do they require starting units and a special amount of resources? or do they play like melee?
None.
The staredit help says that Insane AI will build all unit and technologies, so I presume you would only need a main tech tree building (ex. Command Center, Hatchery, Nexus) and a worker if not four.
None.
The Custom AI (I.E. Expansion Terran Custom, Zerg Custom, etc.) plays like melee. The Easy, Medium, Difficult and Insane scripts, as well as the ones built-in for the campaign maps need more starting resources (usually 3000 of each is enough).
None.