Does thermage and exilis really helps to tighten the skin and increase production of collagen?

Exilis, Thermage or ThermiTight can do a great job of tightening skin on the face and neck. Thermi uses radiofrequency energy to shrink your collagen layer and stimulate the production of new collagen. The new collagen supports your skin, making it look thicker and firmer. You can also further fill out your lost volume with Sculptra — another collagen stimulator — or Voluma, which has immediate benefits. As for a thread lift, you didn’t provide photos so I’m not sure if it’s the right solution for you. The Silhouette threads are really effective at lifting up sagging facial tissues and giving you a refreshed and revitalized look. Consulting with a board-certified dermatologist will help you choose the right treatments.

Thermage works great on the right person for the right reason. The procedure can tighten the "skin envelope" by encouraging new collagen production.
However, each person has different skin health and skin integrity, both of which will affect how effective any skin tightening procedure might be.
Without a personal assessment, it is not possible to advise you; but, definitely any tightening procedure should be completed prior to filler placement in the treated area to avoid disrupting the filler.
Voluma, Sculptra and Restylane can create remarkable improvements, but fillers - and even skin tightening - may be only part of the "fix". If you have excess skin, tightening the area by way of plastic surgery may be another option to consider. Today many facelift patients choose to add fillers to replace volume loss and volume shift.
P.S. Congratulations on your weight loss!

Thermage radio frequency tightens existing collagen and stimulates the production of new collagen to give a firming, tightening and lifting effect.  It does not take the place of a face lift so it is best to have a consultation to see if you would be a good candidate.

In patients with a volume loss and skin laxity, I find that combination treatment using fillers and Thermage FLX works best. I like to use Sculptra to address full face volume loss combined with Thermage FLX to tighten, lift and smooth lax skin. 

Thermage definitely helps to tighten the skin, especially on the face and other areas of the body.  Thermage produces new collagen and improves the aging neck and jowls. Without a photo it is impossible to tell how many syringes you might need or what combination of treatments would benefit you. Sculptra may be a great product for you since you will produce your own collagen and it will last longer. Please consult an expert in lasers and cosmetic injections.  Best, Dr. Green