While for the most part it is only really safe to have one editor use BrezzeCMS at a time, it can be worked around by developers who know what they are doing.
The problems occur are two-fold: conflicting changes, and id generation. While avoiding both, especially small changes can be made simultaneously.
Every developer will understand conflicting changes easily, as it is the same as in coding. Making changes to distinct sections for example should normally work. Or cards and sections, or one changing texts, another editing images.
Breeze generates ids for sections, cards and images in a sequential manner. So two people adding elements of the same category on different machines, will create conflicts that are difficult to resolve. But as long as id's are generated for different elements, no conflict will occur. Also deleting (and as above editing) can be done simultaneously.
So as long as there is only one editor or one translator per language, things are safe. And developers can still make minor corrections while adhering to above restrictions. All in all the restrictions are no problem for the kind of small teams BreezeCMS is made for.