RF microblading - how effective will it be, if at all?

Photos would have been extremely helpful for assessing your particular issues--both front face and profile views.
However, generally speaking the use of HA fillers can work well for all kinds of facial and neck laxity and wrinkles There are HA skin boosters and biomodulaters that can help to improve the quality of the skin by improving its tone, hydration and luster. There are fillers that can address fine lines and wrinkles and there are robust HA volumizing and lifting Fillers for lifting, volumizing and contouring both the face (I.e. a nonsurgical filler facelift) or the neck (I.e. a nonsurgical filler neck lift).
When you write microblading and RF, I presume you meant RF microneedling. If so, this would likely not yield gratifying results. I have been performing manual microneedling (no need for the added expense and risks of RF microneedling) for over 23 years. It is best reserved for treating superficial, skin surface color and texture Irregularities and not for skin sagging and pronounced wrinkling.
You would be wise to consult with an experienced, board certified cosmetic dermatologist filler expert and best of luck.