In order for you to play XCOM 2 on macOS with minimal graphics settings, your computer must meet the following requirements
Operating System:
macOS 10.13.6
Processor (CPU):
2.5GHz Intel Core i5 or greater
Memory (RAM):
8 GB RAM
Graphics Card:
1GB AMD 5750, Nvidia 650M, 1.5GB Intel Iris Pro 6200 (See Notes for more details)
Storage:
45 GB available space