32, saggy loose skin under chin - Do I need a neck lift? (Photos)

Yes, a necklift can help with this. However, if you think you may still have more kids and/or your hormones are still fluctuating (breastfeeding for example), I'd wait until things stabilize out because you will likely continue to have changes.

It is very likely that an anterior neck lift with incision in sub-mental crease (underneath the chin) would address neck platysma muscle bands, laxity, small fat deposits and jawline. In person or a teleconference communication with a board certified plastic surgeon with expertise in this procedure is recommended. Good luck.

You have a few options to aid in this matter of platsymal bands.
You could consider neuromodulators (e.g., Botox, Daxxify, etc) to help and soften the bands. This is generally mildly successful, and always temporary, in nature.
Additionally, SomaCell, is a non-invasive skin-tightening device useful for the submental/submandibular region. There is no downtime or post-procedural restrictions with this option.
MyEllevate is a minimally-invasive surgical option that works well for contouring the neck along the jawline.
Radiofrequency microneedling may help but can be painful and potentially induce pigmentary changes to the skin.
If all else fails, a neck lift is always an option.

Three things can cause a soft saggy neck: extra fat, looseness of the deep layer (SMAS and platysma muscle) and… drum roll… loose skin. The dreaded three signs of an aging neck!
An incision under the chin alone can address extra fat and tighten the platysma… but it can’t tighten loose skin, and it can’t raise up the SMAS.
Tightening the skin and raising the SMAS itself is best done through incisions inside the ear and behind the ear.
Patients who have had weight fluctuations often have extra skin, so a lower facelift, mini lift or facelift which also elevates the SMAS often give superior results.
Is it wrong just to do the neck? No! But patients may want to do the lower facelift at a later date to obtain a more complete result, especially if they lift also want skin removal and an elevation of the SMAS, the deep layer of the face.
So what are the pitfalls to avoid? If a patient tries to solve all the problems with only an under-the-chin lift. The doctor, with all the best intentions, may overly defat the neck with aggressive radio frequency tightening or aggressive liposuction, but can’t remove and lift the skin and SMAS, the neck can still look loose! Why? Because excess skin can’t be removed with just an incision below the chin! And if the beck is aggressively defatted, it may appear ‘stringy’.
So… good results start with a well done nack lift that help the skin as well as the platysma and the removal of the right amount of fat.
Better results may also involve elevation of the SMAS.
And great results, making the face less square and more oval or heart shaped, also treat the midface, the area below and to the side of the eye area… but that’s a whole other discussion!

Based on your nicely post photos, I recommend virtual consultation to vet understanding but would record a full open necklace. Fee range from $8000-$15,000. Best of virtual consult with.