Both methods produce the same results. However, you may find that one suits your design style more than the other. As you become more familiar with creating form designs that have a flexible layout, you will adopt a style that works best for you.
Whichever approach you choose, it is best that you first create a form design that has a fixed layout. You can plan the layout of the form, including all the necessary objects and information that you want users to see. After you create a form design that suits your needs, you can then plan how you will wrap the various groups of objects in subforms and configure each subform to make the form layout flexible. For example, you need to consider which subforms will position or flow content, which flow direction is best for each subform, which subforms will need an overflow leader or trailer subform, and which subforms will repeat, expand to fit content, and break within content.

Approaches for creating form designs that have a flowable layout