For example, airplane mode turns off your internet connection, so your device is no longer constantly searching for connections or communicating with the internet. This means less power is wasted, and more can be used for charging.
If you know you’re going to be using these apps in the near future, avoid closing them. It can actually be more efficient to leave them operating in the background than forcing your device to boot them up again.
Look up the highest ampere rating your device can handle to ensure you’re not wasting money. While using a more powerful charger won’t hurt your device, there’s no point paying if you’re not going to use it.