One of my favorite Mac/iPad features is SideCar. It allows you to easily use your iPad as a secondary display for your Mac.
Setting up With SideCar
There is an icon on top of your main display that looks like an iPad (it may potentially be the AirPlay icon instead). Click on that and you can see a list of devices you can connect to. Select your iPad, and it connects with your Mac either to mirror it or a separate secondary display.
In that same menu, you also add touch bars to different parts of you iPad. Furthermore, you can use your Apple Pencil instead of a mouse or trackpad.