I’m not an expert but I think that the more your suspension compresses (aka softer springs) the more your rear camber will increase as the rear multilink does a great job and it has a good camber curve; with a stiffer spring you have less compression and you probably want a bit more static camber but I might be wrong :)

Roll stiffness for the front is required in a macpherson strut because its camber curve causes it to stagnant or even gain camber during compression. That's why there is a large amount of static negative camber required to offset this. The rear is a different matter, and over all the suspension should be looked at with a holistic approach. It's really not going to matter until you start looking at fine tuning your suspension to iron out certain issues ie. mid corner grip, bump steer etc.

That's true for the rear, but the fronts gain no camber (and actually lose some at peak compression) through compression.

Compared to rears fronts gain a bit dynamic camber when turned from caster though, even if they don't gain from compression. Then again, no that much at small turn angles, which is more common in smoother track driving.

Yeah, people always seem to miss that point. Even for medium speed corners the camber gain from caster is minimal. Personally I prefer to keep caster minimized and if that means I need to add another 0.1 degrees static camber, fine...