The headlines, including yours, imply a President can do anything they want. My reading of the decision is, that it has to be in his official capacities as President. Not anything he does while in office. What is in or outside their capacities as President is kicked down to the lower courts to draw out the decision making even in longer, at least until the election cycle is over. Which is disappointing but not the end of the world, imho.
What is in their official capacities is somewhat defined but has been blurred by previous Supreme Court decisions. Declaring war, for example, is a power left to Congress under the Constitution, but got blurred by the Supreme Court in the case of the Tonkin Gulf when they ruled the President had the authority to react to attack, as fanciful as that attack may have been.
The bigger issue, imho, which they danced around while kicking the can down the street, is the question of what is outside their official capacities, or official capacities they fail to act on? Is calling a Governor and bullying him into finding a few thousand more votes within his official capacity or not? Is sitting on your hands in the oval office watching the Capitol being stormed and not acting acceptable? I suspect the Supreme Court would say this is what the impeachment process is for, which brings the blame back to the Senate for failing to act on the House impeachments.
