Without knowledge of the opening of the multiverse, anyone who has watched the first 'Dr. Strange' or 'Avengers: Infinity War' would easily say that the once and forever Sorcerer Supreme - Dr. Stephen Strange - will easily beat Wanda Maximoff if they were to fight.
As seen in WandaVision, Wanda is unaware of her powers and their limitations. She has yet to realise the full extent of her chaos magic. As Agatha attempts to steal everything Wanda has the potential to do, while trying to manipulate her, Wanda turns the tables and acquires Agatha's knowledge instead.
But with WandaVision's open-ended final scene- where Wanda is seen in her Scarlet Witch attire studying the Darkhold (essentially the necronomicon of Marvel) - this may essentially give her the magical education that made Stephen Strange the Sorcerer Supreme.
The loss of Vision and then her children has pushed her to learn all about her powers and how to channel them. Perhaps, she can learn how far she can go as the scion of chaos magic and what being the Scarlet Witch truly means. It is safe to say that she will only get stronger, truly a terrifying thought, given that she could hold off Thanos with one hand and crush the mind stone with another.
As per Marvel Studios President Kevin Feige, Wanda was the most powerful Avenger even before the events of WandaVision. Nevertheless, this is still a debate, knowing what Sherlock - I mean Dr. Strange - is capable of doing merely with his intelligence and calculated steps.
Dr. Strange no longer possesses the time stone. Does this mean he is easily outmatched by Wanda? Well, we have come to bargain. Dr. Strange does not possess any power of his own. His mind is what truly sets him apart from all other practitioners of magic, his deductive reasoning and ability to invent novel solutions is what allows him to win against seemingly insurmountable odds, especially against entities far stronger than him. Strange always brings brains to a brawn fight and wins, after a fashion.
In 'What If…?' Strange obtains the ability to eat and absorb the powers of his opponents, for example, taking a point blank blast of all the Infinity stones, this essentially guarantees that if Dr. Strange were to become like Strange Supreme, he might just give Wanda the biggest scare of her life. As we have seen in the trailer, Strange Supreme is set to at least cameo in the upcoming Dr. Strange: Multiverse of Madness.
Wanda's transformation into the Scarlet Witch is complete. She is being villainized once again due to how she is dealing with her loneliness and loss. Wanda's grief has already resulted in her unknowingly exerting a level of power that even she does not completely understand.
Like Agatha Harkness whose finger tips became dark during the end of WandaVision, indicating how powerful and dark Agatha's magic is. In the Dr. Strange 2 trailer, we see that Wanda has learned a lot about herself and is becoming more familiar with her abilities. Her finger tips are now dark, for she has started practising all that she has learnt.
The only similarity between the two heroes is that both lack durability and super strength. But the difference is this, Wanda's mental stability is weaker and that influences her focus during fights, whereas Dr. Strange has, relatively speaking, mastered both his mind and body. Dr. Strange's greatest asset is that he thinks of stratagems no one can even fathom, this isn't the first time Strange will magically be outmatched.
If the Sorcerer Supreme and Scarlet Witch were to fight now, after everything Strange now lacks and Wanda now holds, the victor would probably be Scarlet Witch as Wanda holds an evolutionary advantage; the ability to distort and warp reality itself. But as seen in Spider-Man, what if the other variants of Strange were to team up together to take down Wanda? This particular topic will have many more facets once Dr. Strange Multiverse of Madness releases in theatres on 6 May.