About the knowledge consultation of photography theory, if there is an external flash to shoot indoor portraits, don't you need a large aperture lens? If I don't need fuzzy effects.

Of course not. Large aperture lens is an advantage anytime and anywhere. Modern SLR uses full-aperture photometry to focus, and a large-aperture lens will get more full light than a small-aperture lens, so a large-aperture lens is obviously brighter, faster and more accurate than a small-aperture lens, and it is easier to focus in a dark place.