If you have the deLuxe edition the only thing you will notice is that the launcher has Horizons as well as the base game. The "goodies" in the commander pack are in-game assets - repaints for three types of ship (Sidewinder, Viper Mk III and Cobra MkIII) - so you only see those available when in the livery screen when you are in one of those ships.
Here is the frontier store page for the DeLuxe edition showing you the details:
Elite Dangerous: Horizons is becoming FREE for all players on 27 October 2020 via an update to Elite Dangerous. Th
www.frontierstore.net
... and here is the page showing what is in the Commander Pack itself:
www.frontierstore.net