You can do 1 by setting boot-args to a certain value [1]. But even then it's not the cleanest experience since you have to start in clamshell mode and then open

You can do 1 by setting boot-args to a certain value [1]. But even then it's not the cleanest experience since you have to start in clamshell mode and then open the screen. And if the computer goes to sleep the effect is lost. [1] https://apple.stackexchange.com/questions/152203/turn-off-macbook-pros-display-while-connected-to-external-monitor-on-yosemite https://apple.stackexchange.com/questions/152203/turn-off-ma...