There are different ways of doing this. In our projects we always form vertical teams that include frontend and backend, but I know of other companies that use the micro frontends architecture only on the frontend level where all frontends talk the same backend or a cluster of services.
We believe that it's a good thing to make teams as cross-functional as possible. Our ideal team would also be able to make it's own business decisions in the area it is working on. Here is a link to a diagram that illustrates the different "depths" you can can aim for.