The model has too much muscle mass

Don't add too much muscle shading. The amount of muscle and the complexity of the shading in the rendering are related. Also, normal rendering will reduce the appearance of muscle mass.

Choosing an Asian nationality will make the muscles appear less prominent. As long as the face for face-swapping is from a European or other nationality, the final result will still retain the characteristics of the reference face.

Try to select a younger age. Older or middle-aged models tend to have larger muscle mass.