Would subcision alone minimize the appearance of a scar on my nasal bridge or should I consider adding filler as well? (photo)

I'm sorry you have this problem. As my regular followers well know, I have been cautioning them for years to exercise a great deal of "buyer beware" when being hawked expensive, laser, RF or other so-called light and energy-based devices owing to their unproven or variable results and their risks, such as scarring and permanent hypopigmentation, as in this case. Sorry.
From the photo provided, in the hands of an experienced, board certified cosmetic dermatologist scar treatment and filler expert, subcision accompanied by the use an appropriate HA filler would be a very reasonable approach for elevating and smoothing the scar. As this appears to have precipitous, broad "shoulders,," this may also require light cautery treatment or the use of an appropriate peeling agent to create a more rolling border. Once the scar base is elevated appropriately, the hypopigmentation can be addressed with by professionally performed, manual Dermastamp microneedling (no need for the added risks and expense of RF microneedling) accompanied by the topical application of Rx pigment enhancers. Hope this helps and best of luck.
Make sure to consult with a board certified

Our treatments use combination therapy to improve the epidermis and dermis for most deep scars. The options available for acne scars depend on the character of your scars, in terms of topography and contour. We see atrophic and hypertrophic acne scars, as well as scars that have hypo and hyperpigmentation. We begin each scar evaluation with an assessment of scar quality and subtype. Our main concern is rebuilding collagen and that is why we use a HIDEF protocol that includes combination therapy. Morpheus 8, scar subcision, fibrous release, fractional laser, CO2 laser, Thulium laser, PDL Vbeam laser, and fractional resurfacing can be used in addition to TCA Cross and chemical peels to further improve skin. Patients should start Melarase AM and Melarase PM for active hyperpigmentation. Always begin with a consultation to decide whether early subcision should be started.

Best,
Dr. Karamanoukian
Realself100 Surgeon