"A mode for Keyboard and Mouse; this is where the mouse only turns the ship, and the guns fire toward where the ship is facing."

By default, you will notice flying the ship with a mouse means that you need to recenter the mouse manually when you wish to stop turning. For me, this often leads to over compensating my turns and a difficult time tracking my target.

Ctrl+C will toggle relative mode, which will anchor your mouse to the center of your screen. This will make it MUCH easier to keep a target in your sights.

The downsides to having Ctrl+C enabled is that, your guns are locked to the center of your screen, this is perfectly fine if you only use fixed weapons, but it means your gimbaled weapons will also be fixed to the center. Your turning speed is also tied to your mouse sensitivity so at low sense, you won't turn as fast.

To combat these issues, I have set the toggle to one of my extra mouse buttons, that way I can unlock my gimbaled weapons or make sharp turns when needed.

As for the CAPSLOCK toggles, here is my understanding for those:

Comstab: When enabled, your ship will prevent you from sliding while making turns. This could be useful if fighting in a densely littered area where your momentum could easily make you slide into an asteroid or something if you're not careful. Personally I just use the booster on my Avenger to cancel out my momentum, but that only works well for me because the booster is unlimited, if it gets limited without regeneration, I suspect I won't be wasting it on this as much. When Comstab is off, you will continue moving in the direction that you put thrust into, even if you turn your nose elsewhere, until you reverse thrust in a different direction.

G-Safe: When on, this will prevent your ship from making turns so hard that your pilot will black/red out. When off, you will be able to maneuver better but risk red/blacking out.

Couple/Decoupled Toggle: "Coupled / Decoupled Mode. There are two flight control modes, coupled and decoupled. In coupled mode, flight is always nose-forward, like an atmospheric jet. When turning, the ship continues to move at a set velocity in the direction the nose is pointing. While in coupled mode, you can strafe side-to-side (Q and E) and upand-down (R and F). When coupled flight is disengaged (decoupled mode), the direction and speed the ship is moving at is essentially “decoupled” from the nose direction, allowing the ship to rotate freely without changing the direction of flight. When in decoupled mode, the ship is allowed to strafe forward and backward, side-to-side, and upward and downward. When coupled mode is re-engaged again, the ship will begin moving at the current speed but in the new nose-forward direction. This mode is indicated by the “COUPLED” indicator on the HUD."

Here is a guide to all the controls of ArenaCommander: https://robertsspaceindustries.com/media/ul658xbb329tfr/source/AC-Manual-09-V7.pdf