It will not be possible to disable budget optimization for new and already launched campaigns.

What to expect

Campaign budget optimization allows you to set up a total budget for all ad groups included in the campaign, and then automatically reallocate it in real time to the most effective ad groups.
This will allow us to achieve better results with the available budget and thereby reduce the overall price for the result.
Optimizing your campaign budget can bring more results at a lower cost.
When using campaign budget optimization and the lowest bid strategy, you can get the lowest price for the result within the entire campaign, not individual ad groups

And one more thing for those who like to delete information.
Now you can delete a message on FB for all participants in the chat/conversation, the main rule is no more than 10 minutes after sending it.