Final Fantasy XV won't allow you to customize a lot of different options associated with the gameplay, although it gives access to two types of combat - Active and Wait. Active is the default type. When it's selected, the combat will take place in real-time - you won't be able to active an active pause that allows you to plan your next move without the enemy interference. With Active mode you can only stop the game by bringing up the inventory/main menu screen. This makes the combat a lot more dynamic, although Wait mode is still the one you should be using.
In Wait mode combat also takes place in real-time and looks almost exactly the same as with Active mode, but comes with one significant difference - once your characters stops (when Noctis is not moving or performing any action) the game will enter the active pause mode. During it you will be able to freely look around the battlefield to plan your next moves. The game will resume once you perform any action and will pause once you stop moving again.
Changing the combat mode is trivial. You only need to get into the game, activate Options and enter the Combat tab. Inside you will find the option to change combat from Active to Wait, or vice versa. You can change it again at any given moment and you won't be rewarded or punished by using any of them. It's only a matter of personal preference.
Wait mode gives you more freedom in combat and makes encounters a lot easier, especially because it allows you to use Libra. This ability allows you to scan enemies to learn about their health points and their weaknesses - which weapons/elements will be effective / ineffective against specific foes. More on that can be found in "Libra" chapter of this guide.