Well, both are responsible for creating Movies and TV shows. Marvel studios is the huge production company founded in 1993 and current president is "Kevin Feige" behind all movies and TV shows, Marvel Studios hires specific Directors to bring epic tone, style and direct the Actress in the individual movies. While Marvel Studios still controls and decides the big stuff such as:- "What movie gets made, how should it connects to other movies, and what are the overall story is". They still control the Universe by creating their own vision and storyline in the individual Movies or TV shows. They also create Rules that Marvel Directors must follow while making the Movie. They owns the rights to Marvel characters and comics, and also handle all aspects of filmmaking. Marvel Studios is the major reason for creating big plans and connecting story lines to make the movies.
Marvel Directors:-
Marvel Directors which are hired by Marvel Studios are the responsible for making good styles and designing the tone in the Movies or TV shows. They follow all the rules made by the Marvel Studios and bring each individual Movie or Show to life. They hires the Actors with the help of Marvel Studios itself and tries to create their own different art of vision while making the movies. They Plan action scenes, Emotional moments, and Visual styles, Their job is to bring a Marvel story to life while still following the regular Marvel’s plan. If their own vision doesn't fit in movies, Marvel can stop or change it. If certain Directors become popular due to their creativity, They get trusted with bigger projects later.
Conclusion:-
By all this info, we can say that Marvel Studios and Marvel Directors work hand-in-hand to build the Marvel Cinematic Universe! They both have their own work and support to make Movies and TV Shows. And also it has announced that the credits for Marvel Studios' Avengers: Endgame list over 3,000 people. So by this, we can understand that for every Movie, there is extremely huge team that works on it including "Marvel studios" itself.