Got any links or a blog that consolidates your findings? I love learning about gnarly hardware, and yes, Saturn takes the cake there. Dual SH2s and VDPs, with scaled sprite quadrilaterals for polygons... what a nightmare!
I absolutely love this series, the author goes into so much detail.
Jo-Engine: http://jo-engine.org/
A fantastic, FOSS SDK for the Saturn, allowing excellent programming in C with management for sprites, collision, etc.
The Rockin-B: http://www.rockin-b.de/saturn.html
Original Sega SDKs, including SDL and more.
Fantastical resources for plain C and/or Assembly-based development.
These should get any aspiring beginner or experienced developer with previous console experience moving quickly in the right direction. :)