Are Challenges / CAPTCHAs on by default? I see in the article reference to specifying what kind of challenge in the context of Firewall Rules. But what happen

Are Challenges / CAPTCHAs on by default? I see in the article reference to specifying what kind of challenge in the context of Firewall Rules. But what happens if I’m a new Pro customer, are Challenges on by default? Said differently, if I sign up example.com on a Pro plan and make no changes to my settings - would potential users who visit example.com be Challenged?