Do daily ED drugs (e.G., Cialis 5mg) work as well as single use ED drugs (e.G., viagra (sildenafil) 100mg, Cialis 20mg)?

Maybe. The dose of Cialis for erection is either 20 or 10 mg. The 5mg dose is usually for benign prostatic hypertropy. There is some cross-over at 5mg to help some erectile dysfunction.