It's unlikely to matter how many units you take as long as you finish your prereqs. The difference would probably be in which courses you decide to take. If your choices are a 6 unit genetics class or a 3 unit art appreciation class then it's obvious which looks better even if neither are required. But if it's a 3 unit intro to parasitology verses the genetics class then it doesnt matter, because they have no idea which class you had the option of taking and didnt and the class you did take would be very appropriate for a pharm applicant. In the end your overall GPA would be more important.
To answer the other question, I doubt what I call academic efficiency matters. I've taken as few as 7 units a quarter and as many as 16. I'll have almost 250 unit hours by the time I'm done. I've applied to four schools gotten two interviews so far and haven't been rejected by the other two yet. I didn't even bother with the PCAT, just applied to schools that didn't require it. So if it takes you 8 years at 12 units/semster (my average is actually 16) it doesn't seem to matter as long as you meet the prereqs and have a decent GPA (3.49sci/3.59cum) and good LORs (haven't seen them, but I hope they said good things😉 )
