Can I join using a different email than used during registration?
Yes. You can join using any email address you own, or by connecting to one of the available other options such as Garmin and Strava.
When you join an event you are typically asked to provide a verification code and this is the unique data that will connect your profile with the registration data from the event.
It is not uncommon to have multiple family members register with the same email address, but each will receive their own verification code from the event organizer. Each family member will also create their own account and then enter their own verification code to 'claim' their spot and join the event.
Emails that are triggered based on the performance during an event (such as badges and completion of a challenge goal) will be send to the email as used during the registration (when this data is imported by the event organizer).