For how we live.
Both brands sell drug-free external nasal dilators with much the same evidence behind them. The differences are range, materials, and the fact that only one also sells a mouth tape.
It is a strip of tape over the lips at night, meant to force nose breathing. The idea is simple; the safety caveat is the part that matters most.
The sinuses really do produce nitric oxide at concentrations far above the lower airway. Whether routing more of it through your lungs at night does anything measurable is a separate, unanswered question.
Trials measuring it are small but consistent: nasal breathing lowers peak oxygen uptake and feels harder at intensity. The interesting findings sit at submaximal effort, not maximal.
Breathing through the mouth in sleep tracks closely with sleep apnea severity. The direction of the arrow is the part the research has not settled, and it changes what any intervention can claim.