What actually happens after running the "disable directory synchronization" powershell script?

LainRobertson Thank you for your response.  We are first disconnecting the device from the local domain then joining to AAD before we convert to the account cloud-only. That has been very smooth so far with no issues.  Since we cannot do this for all devices/employees at once (we do not have the resources to do so), we needed to do this one by one by one.  

The passwords from our local AD server do sync to Azure as currently if a user is still set to Dir Sync Yes in AAD we have to reset their passwords on the local AD.  

I've contacted both O365 support and purchased support from Azure as well and no one can us a straight answer instead of "run the script and hope for the best" type of reply.  

If running this script causes the same issue that I had with one user where they lose all of their private channel membership and now have 150 users to manually have to fix, we will not be able to run our business.  We are heavily on Teams now and it's a scary situation to not have anyone at Microsoft able to help or guide us.  

I can't even get a single powershell script to export all private channel memberships from Teams (I've tried 10+ ones I've found online but they only seem to work if you run it by each team/channel combo by name).