@Olo To add on to what others are saying, I feel like “femgaze” stuff tends to go out of its way to really describe the giant and things like his status, personality, level of attraction, etc. That tends to be ignored in “malegaze” content, which is understandable since the appeal comes from the shrunken woman.
And that’s not to say femgaze creators just focus on making the giant hot. There can be a lot of variation- the context and motive is what’s truly important. He could be a shy, nerdier guy desperate to have a certain woman to himself. Maybe he’s wealthy, powerful, and handsome- he doesn’t NEED to do the whole shrinking thing, but he does it purely because it’s enjoyable for him. Or maybe he’s just an average dude that’s just trying to help the best he can.
Of course, this can also apply to superficial things like hair and eye color and stuff. I love being able to visualize what the author is intending. But you can definitely leave physical descriptors open to interpretation as long as you convey things through his attitude and relationships.