Reports claim that the current Netherlands coach will be confirmed as David Moyes' successor early next week - and the deal could even be announced over the weekend.
But both Soriano and Scholl - who worked with van Gaal during his time at Barcelona and Bayern Munich respectively - have issued warnings over how the 62-year-old works.
Former Germany midfielder Scholl, who was reserve-team coach at Bayern under van Gaal, does admit that the Dutchman gets results and even calls him a 'genius'.
"He's very strict and severe. So the players just have the chance to follow him or they are out, and he takes the next players," Scholl, who is now a TV pundit in his homeland, told The Guardian.
"He's very good with young players. I think everywhere he was, he had some problems with big players and the staff."
Scholl explained how he feels van Gaal approaches a new squad, adding: "There are 26, 27 players and he is looking for the 14 to follow him – 14, 15, 16 to follow. His thing is not the motivation [man-management]. He's good in motivation, but this is not his main character thing.
"His thing is really working on the pitch – that's brilliant. And that's how the players learn. You know by yourself that if you learn from somebody you are curious, you want to learn more."
Scholl even thinks the senior players, such as Wayne Rooney, may struggle to adapt.
"Some of the players, I can tell you, like Rooney, I don't think he has to learn anything more. So that will be difficult for him if the coach says: 'You have to do it in a completely different way. Whatever you did until now, change it.'"
However, Scholl does not anticipate Robin van Persie having any ongoing issues with his national-team boss, adding: "The thing van Gaal teaches is the same thing van Persie learned from the very beginning. So there, I think, there will be no big problem. Of course, he is a big player but he is a Dutch player. That's the thing, and the difference to Rooney.
"For the big stars, it is not easy to work with him but for the young players, he is brilliant. He is brilliant on the pitch and wants them to learn all the time - even the old players."
Scholl does not see van Gaal staying for an overly long time at Old Trafford but he insists that he will turn things around for United.
"He's a brilliant football coach. The way he likes his team to play is absolutely. His main thing is to keep the ball, to be proactive not passive. He is a genius, he's one of the best I've ever seen on the pitch," said Scholl.
"I think, for the moment, he's exactly the right coach for United and United will be successful again with him. That's without doubt. That will come. The thing is, he wants a lot of things from the players and, for the players, it is not easy to satisfy him all the time and so after several months, one or two years, it gets less what the players learn.
"We're not computers. Sometimes the brain is full. And he still wants [you] to learn, to learn, to learn, high level, every day. Is it annoying? No. It's exhausting. They lose power. That's what happened at Bayern Munich.
"And that's why he often picks young players because they learn and learn and learn. I don't know if he is working still the same. I just can tell you what happened in Bayern Munich."
Manchester City chief executive Soriano witnessed first-hand how van Gaal worked at Barcelona, and speaking prior to David Moyes' sacking at a business leadership conference in Abu Dhabi earlier this year, he stated the Dutchman had a 'difficult style'.
“If you treat your people bad, they remember. One day you make an error and they kill you. I’ve seen this in many clubs. Louis van Gaal has been a very good coach in many clubs but his style is very difficult. The same thing happened to him in Barcelona as in Bayern Munich," said Soriano.
“He is very tough, people don’t like him, but he wins. And one day you don’t win – and when you don’t win, everybody that is angry with you will come back to you and try to kill you. In the movies this works, in real life it doesn’t.
“One thing I have learned in football is that leadership is a very difficult thing. You need to choose your leadership style based on what your team needs, not your character. This is counter-intuitive.
"People think a good leader is someone with character. I say a good leader is someone who can listen to the team, understand the kind of leadership a team needs and apply it.”