You can create the relationship, but ACF will not do the work of returning the posts for you. For example, you can create a taxonomy field to select the category then use the value of the field to do a query to get the posts. Then you can use the results of that query to build your “Grid”
You might also use a relationship field, this would allow you to select the specific posts that you want displayed rather than a category and this would return a list of posts and then you could use this list to build the grid.
ACF does not provide any “Front End” functionality except for the ability to get the values of the fields that are saved.
