PEP or OPEP devices provide improved mucus clearance and airway defense.
However, they have little or no long-term effect on respiratory muscle strength. The respiratory muscle strength provided by the Breather improves immediate and long-term cough capacity, which will be more effective for unassisted long-term airway clearance than PEP/OPEP devices.
These PEP/OPEP devices may actually be good adjunct devices for The Breather, as it may help loosen the mucus, while RMT is helpful to effectively excrete the mucus due to improved cough effectiveness.