I agree that the decisions could be more linear. Most inexperienced off-roaders (including me) don't think too clearly when it starts to get hairy. The manual really does need to be better. Probably vague for liability reasons.
It all comes down to getting good tires. If you do, then you have a little more allowance in trying out different off-roading scenarios. Tires are the cheapest, yet most performance-enhancing mod that you could ever do to your 4Runner. Point being, with good tires, you can play with the settings without any serious risk, and see what you prefer and what works best. There is no substitute for first hand experienceimp: