How Effective is Photomodulation (LED Skin Treatment) for Skin Tightening?

LED doesn't work for skin firming or tightening. LED treatments are really great for surface rejuvenation of the skin, but won't help much for tightening loose or sagging skin. It really takes a deeper heating element, such as from ultrasound or radiofrequency to achieve more of a tightening effect. For ultrasound devices, we use Ultherapy to tighten the neck and the face. Radio frequency devices include Exilis, Pelleve and Thermage, all which could be used for skin tightening on the neck and face, as well as the thighs and abdomen for some of the devices. 

LED treatments are an excellent way to stimulate the skin to refresh itself by "super-charging" the cells and speeding up repair mechanisms. Because it is a minimally invasive procedure, a series of treatments is ordinarily required to get any visible results. Certain LED lights and settings are excellent for enhancing the penetration and effect of anti-oxidant topical medications. as far as skin tightening is concerned, I doubt that LED is going to give you enough change in the health and fitness of your skin to see real skin tightening.
Currently, there are only 2 primary non-surgical means of skin tighenting: Thermage (results are very variable and usually mild) and laser resurfacing. Fractional laser such as Fraxel can give very mild tightening and full classical CO2 laser can give very good facial skin tightening but requires a long healing and recovery phase.
if skin tightening is your primary goal (because you have laxity in cheeks neck or jowls) your best results are likely to lie with a surgical approach: facelift or neck lift, even a minilift if your laxity is mild.
unfortunately, despite the proliferation of non-surgical treatment, non of them measure up to surgery for skin tightening.
if i were you i would get a consultation with a good plastic surgeon who can examine you and outline your options. if you want to stick to nonsurgical options, see if thermage is an option and if skin texture issues are also a concern add Fraxel laser resurfacing. if those options are too mild for your situation, consider surgery.