Romulans and Tholians are Xenophobic races, they will not expand like the other races. Also an AI starting point will effect its ability to expand.
The Minor races, (Hirogen, Gorn, Kazon, Son'a, etc) all share the same AI files so they will expand and react simularly.
In an even playing field with settings set to medium and each race using its 5k EMP file, they will ALL expand well and be very difficult to beat. I do not use cheats and I recommend that you do the same.
The best AI race in the end has typically been the Klingons. The Borg a tie with the Cardassians. The federation and Ferengi tie, and so on.
It really depends upon the AI's starting location.
As for the mine issues, that is an issue with SEIV not the mod.
