Which microneedling for skin firming?

A photo would have been extremely helpful. What I can say, however, is that in the hands of an experienced injector, the use of robust HA fillers can volumize the cheeks, diminish smile folds, treat tear troughs and infraorbital hollows, define and straighten sagging and jowly jawlines. The results of filler treatments are typically immediate, engender little to no significant downtime, and elicit a "Wow!" response.
What I can also say that is that, unfortunately, the hard science to support the use of so many of the expensive, "bells and whistles fraxel laser and RF devices, lags well behind the heavy marketing hype and social media buzz for these all-too-often, here-today-gone-tomorrow, fancy-named gizmos. You would be wise to exercise a healthy dose of "buyer beware" when considering these and to consult with an experienced, board certified cosmetic dermatologist. And, finally, one more piece of advice. Don't go into a consultation asking for a certain device because, to your later frustration, disappointment and waste of money, you are likely to get what you asked for. Hope this helps and best of luck.

You may want to consider Morpheus8. This treatment combines microneedling with RF technology to improve overall skin tone and texture. Three sessions are recommended for optimal results. See my website or a provider near you to learn more.