I noticed if you run a trigger for player 1 and have it create 1 unit; it will only create 1 unit. However if force 1 contains 2 players, it will create 2 units. Is there a better explanation on this mechanic?

I'm having issues when I want to create a unit and have a sound wave play at the same time without having to create two separate triggers.

Creating triggers under "Force #" (and sometimes "All Players") is a massive time saver when it comes to high-complexity maps.
What is does is create an imaginary duplicate of that trigger for every player in the Force. Whenever one of those players meets the conditions, it will fire. If X number of players meet the conditions at the same time, the trigger will fire X number of times. This mechanic's usefulness increases further when employing "Current Player" conditions. This allows the trigger to become completely player-independent, which means that each player's imaginary instance of the trigger no longer interferes with other player instances, especially important for things like Create/Remove/Set/Add/Subtract (i.e. whenever quantity matters).
You will find that "Force #, Current Player" triggers are superior for basic map functions like menus, shops, items, and various trigger abilities/skills.

If a trigger is owned by a force, each player in that force will run it once.