It would be very difficult to describe your neck as too masculine, based on these photos. I do not see much to be done to soften and feminize it. Small augmentation of the breasts and augmentation of the hips with fat grafting may give you more feminine look all together, if that is what you are...
You cannot evaluate the sagging under the chin alone. Because this is usually the last step of sagging in other parts of the face. In addition, chin stretching may cause sagging under the chin itself. Please, if you share full photos of your face here or in private, a full diagnosis can be made.
For unique cases where a variety of modalities could be used to treat the condition, I would suggest an in person or virtual consultation to develop a custom and effective treatment plan. It is difficult to precisely define the best option without collecting the same information. I suggest...