It is highly unlikely that Garnacho will go to the Saudi pro league and he will just be the laughing stock of many when he gets here. He is still very young and is actually quite promising as long as the team he plays for gives him more opportunities. But even at Manchester United he experienced ups and downs in performance so many people doubted him.
Agree. Even if there are many Saudi teams interested in him and want to pay him with huge salary, Garnacho must choose to stay in Europe. Garnacho must be aware that he must play in the best leagues in the world to improve his ability. If Garnacho joins Saudi league, his ability won't increase massively as in the European leagues. Although Garnacho decides to leave Man United, I think he will move to La Liga or Serie A only.Maybe Al-Hilal's offer is as big as other Saudi pro league teams. But if he had to go to the Saudi pro league, wouldn't it be better for him to go to his idol club, namely Al-Nassr, rather than Al-Hilal? 
It is good that he may play together with Ronaldo in Al Nassr. But he won't improve his ability and skills if he joins Saudi league. Now, he won't consider to play in Saudi league, he must focus on playing in European leagues.Well, however, this is just a rumor and with Manchester United he still has a lot of work to do and even if he feels like leaving there it should be to another European club that can make him more comfortable. 
Yes, it is just a rumor. In fact, Garnacho is very needed for Man United. Garnacho contributed a lot for Man United, he becomes one of the mainstay players in Man united. I guess Garnacho is still very comfortable playing with Man United. Ten Hag won't let him leaving because Garnacho is still a part of Real Madrid squad for the new season in UCL.