For right clicking, there are two ways when using the trackpad
- Control-click, i.e. tapping the trackpad while pressing Control key
- two-finger-tapping
Can they be used exchangeably?
If not, when to use which?
Yes, they can be used interchangeably. The two-finger tap is a shortcut employed by OS X for more convenience / accessibility, however, it has exactly the same function as the control-click.
In most apps, macOS treats Control-click the same as a right-click. However, some programs such as games and virtual machines listen to the keyboard not as a series of keystrokes but as whether each key is held down at each moment. These programs will receive the Control keypress and the left-click separately, without macOS transforming them into a right-click.
So feel free to use Control-click in most places if that’s easier for you. However, when playing games or using a VM you might have to use the two-finger click for the program to recognize it.