It doesn't matter, and you're understanding the problem wrong. 

The game design is overambitious for the Iron Engine (game engine).  The game is constantly becoming cluttered up to the 2 gig limit, and creating instability, crashes, and slowdowns.  Aside from that, the game is only capable of utilizing one core of a processor.  The game engine was written in the mid 2000's when multicore processors weren't the norm for PCs (they were still separate physical units).

The simulated game speed (commanding the game to increase game speed) is different from the actual game speed.  You get diminishing returns the later you try to do this during a gaming session.  You don't really get any gain for slowing it down nor do you for trying to speed it up later in a session.  There's just too much going on for the engine to handle.  This exact same problem can be seen in the original Supreme Commander seres (which was built with some multicore support, albeit very poor).

The only real solution to this (aside from not playing on needlessly large maps) are almost all in mod form.  Using TSOP (https://forums.sinsofasolarempire.com/428154/page/1) will get you about as much as one can out of the engine.  Flagging your .exe for LBAA support also helps.