I have used "dual therapy" for ED, mainly caverject plus Cialis, although also Cialis plus Viagra.
I have not had any problems doing this but my doctor and specialist advise against it. However, the caverject and Cialis remain on my repeat prescription list so maybe that is some sort of acceptance.
I have tried Muse in the dim past, it burns, and didn't work that well for me. We all vary however.
20 mg is the maximum dose of Cialis, lower doses may not be effective.