RFCM only includes BBAI speed tweaks, as I wanted to keep RFCM same as original, just faster & with more speeds.
SoI includes more AI-related BBAI code, though it's still maybe 1/3 of the whole thing. Too much of BBAI is irrelevant for RFC, i.e. the AI strategy overhaul, which makes it more aggresively towards a specific victory conditions like culture or space race. The things that work in SoI are some worker AI stuff, city management improvements, better wonder building, handling of stranded units.