edit efivars on MacOSX
Yes and no.

Full access to all efivars is not that feasible or easy in macOS / from OS X.

But if you want to achieve the goals from the link and command you cited then go here please: GPU problem - Boot Hangs on Grey Screen 

There you will find the equivalent for a pure Mac environment:

nvram fa4ce28d-b62f-4c99-9cc3-6815686e30f9:gpu-power-prefs=%01%00%00%00


Read the whole guide, though. It's still a bit of a dance to apply that variable and manage the consequences of it.