This is the story of my game of Civilization IV Adventure Thirty-eight from Realms Beyond Civilization.
I do know what a Rainforest map looks like - I was playing with it for a game I was thinking about sponsoring. It is of course a perfect map for a high-food variant, being almost all grassland underneath jungle, with lots of food resources and rivers.
So I have two bits of pregame planning, one general and one specific.
Generally, we will need a dense city build. More cities mean more units allowed. Cap space will be tight, so more cities with lower populations is the way to go.
Specifically, we need the Pyramids, and I'm going to try this plan. Oracle to Metal Casting to whipped forge to Great Engineer the Pyramids. I've never done that one before.
A few more assorted thoughts: Once the Pyramids are in, our research rate will be very independent of the slider. I can go straight to Drama and the culture slider for happiness. I would also like to acquire a vassal, both for happiness and for a guaranteed diplomatic vote later. So what's the best tech point to conquer an AI using few units? Assume no siege, or at least just bombardment siege and no suicide. I guess Tanks?
"Slavery vs Caste?" That's easy. Slavery. Two scientists is plenty of specialists early, and adding two merchants at markets is enough for the middle game. The specialists are pretty much the same in economic productivity; the beaker-gold skew effect does exist but is usually minor. Also, the Imperialistic trait means WHIP SETTLERS. (Food invested into a settler doesn't get the +50% bonus. Settlers are more expensive if not whipped.)