Pardon me if it's something obvious, but what exactly is the "Navigation Style" option? What does it change? I tried changing it but I remain confused.

What about the "movement indicators"?

The movement indicators are visible arrow at the side of the screen when you move the mouse left/right/up. They show that clicking there will either look or move.

The navigation style is based on this.

Swipe & push - You can drag the screen left/right to look and drag down to move forward, or click on the side of the screen where the indicators were shown.

All other options are variants of these. ie: Swipe only, push only, press to look and swipe to move.