In case you want to update a flow which is used in an embed you have to consider a few things:
As long as you don't sync the flow in the embed settings, your users will keep using the previous version. Thus you can draft your flow without breaking existing flows of your users.
The existing flows for your users will not be able to have different Connectors that require authentications than they had before. However, you can remove Connectors which previously needed authentications.
Once you sync your flow changes it will immediately apply to all existing flows and all future flows created via your embed.
You can sync a flow by going to the embed settings, opening the embed edit dialog and pressing the Sync button below the flow which you want to sync:
Syncing an embed flow
The flow will be synced one you click the button, even if you not click the Submit button of the embed edit dialog.