Jira workflow questions and past request

[Raymond Correa]

We are looking to change some Jira workflows for a project and had a few questions. 

Is it possible to either pause/disable all user notifications for closed/completed tickets? When we initially tried change the workflow it reopened up every single case that was closed/resolved and the queue got over 1000+ tickets reopened. Not sure if that was due to workflow change and or switch schemes that I accidently did ? We would like to bulk close these cases without the users getting swapped with notifications 

Another question if we do change workflows again will those closed tickets status get changed and get reopened up again as well? We would like to make the change and prevent all of these tickets be reopened again and flood the queue with old closed out tickets. Any ideas on how to approach that?

Appreciate the help on this.