We are all different. Buy a small box and see if you notice a difference. Research NIH studies. You'll find more suggestions there for other herbs. Just don't be scammed by some of the advertised stuff that wants to charge you an arm and a leg.
Drinking any tea can provide expectorant benefits as warm liquid helps loosen up phlegm more than cold or room temperature liquids. Still its important to drink half your pound weight in ounces of water everyday but drinking that much tea is not good for you. Beside ridding your body of toxins, lungs are about 83% water so It's really important to stay hydrated.
https://copd.net/living-with-copd/pulmonary-rehab/weight-management/hydration/