I have used many MAX7219s in designs, with SPI.transfer() for sending it data.
The LOAD pin acts as an active low chip select.
digitalWrite (csPin, LOW);
digitalWrite (csPin, HIGH);
MAX7219: "Load-Data Input. The last 16 bits of serial data are latched on LOAD’s rising edge."
MAX7221: "Chip-Select Input. Serial data is loaded into the shift register while CS is low. The last 16 bits of serial data are latched on CS’s rising edge."
So for the MAX7219, you could do the 2 SPI transfers and then toggle LOAD from Low-High-Low.
while for MAX7221 you need to drive it from High to Low, do the transfers, then bring it back high.
The MAX7219 also works properly with the same sitting at high, bring low for the transfers, then bring it back high.