For example, if I sent out 8 emails in a campaign, can I find out the average number of emails the unique subscribers opened?
If you do an Email Perf report, for 8 emails, you can see an avg open rate or count. Not unique.
In RCE, I believe it is unique.
Smart List will give you a list of people who Opened at least one of the emails.
Yes. Run a lead performance report grouped by email address - filter to leads sent the emails you want to report on. Use a smart list custom column for each email open.... You will see which emails each individual opened. Export to Excel and get your average opens per lead.