Can I limit the number of push notifications received by a user?Definitely, it's possible to create global capping rules on all notifications to limit the number of push received during a given period.
How to use the TTL option?You can set an expiration delay or a Time to Live (TTL) , globally or per campaign.
How can I cap the number of themed notifications received by a user?Indeed, you can add labels to a campaign to set a capping on the number of notifications received per user and label on a given time period.