MacBook Pro 2016 to 2020: four Thunderbolt 3 ports four 4K displays.
MacBook Air 2017 to 2020 and later: two Thunderbolt 3 ports two 4K displays.Apple allows Intel Macs with USB-C to support one, two, or four 4K monitors plus one additional or if there’s an HDMI port, as on the Mac mini, one via Thunderbolt 3 or USB-C and one via HDMI.