Q: 

When looking at reports in emails - people who have opened the email. Can you create a task/ lead for all at once rather than individually?

A:

Yes you can and the way to do that is as follows:
1. Create an automation within which you add step actions for immediate task and immediate lead. Start the automation (empty of contacts)
2. Filter the opens from your email report by Select All then Add to Group
3. Add your new group into the prepared automation!