[Too]

This isn't just a thought experiment. This is genuinely what driving on Autobahn is like. You might think you are overtaking fast in 150kmph but then theres an even crazier guy coming in 200 behind flashing you for going too slow.

Both alternatives are equally common, either you slow down to 60 and let the 200 car pass, or you stay in the overtaking (maybe speed up a bit of of courtesy) and let the 200 guy slow down. In my experience the faster usually has higher priority unless the traffic is very heavy, because by going faster they also disappear faster and don't hog the left lane for as long as someone overtaking at a slower speed.