Sit where ever and how ever You feel the most comfortable. Every person is a different shape, size, weight. Some have back problems, others short arms.
Your putting way too much thought into this.
The lumbar is pretty self explanatory if you play with it. One way deflates the rest inflate.
Only thing i can suggest you to do is increase the side bolsters or as you call them "wings" when you want to drive aggressively, other then that sit where YOU feel best with whatever lumbar you need.