#2 Drastically changed the style of play
Manchester United under Mourinho had a very pragmatic style of play. Caution before risk was the mantra for the Portuguese boss. But under their Norwegian boss, The Red Devils seem to take more risk and free-flowing football.
In many of Solskjaer press conferences, the Norwegian has emphasized the fact that Manchester United is all about taking risks. Clearly, that is shown on the pitch. In his very first match, Manchester United scored 5 and their 3rd goal by Anthony Martial was a proper old school Manchester United goal, filled with swagger and arrogance.
They don't keep all of the possession, but what they do with the ball is what matters. Those old school Manchester United counter attacks can be clearly seen. For example, see the goals against Arsenal, Tottenham Hotspurs and Chelsea. All of them have been pacy, direct and slick counter attacks.
Manchester United under the Norwegian is looking a much more fearsome outfit. Right now, no defense would like to face an attack of Romelu Lukaku, Marcus Rashford, Paul Pogba, Anthony Martial and Jesse Lingard.