SN74CBTLV3257

it is neither one. If (make before break) or (break before make) is designed in it will say it in the datasheet.

I'm sorry, but doesn't it have to be one or the other?  Either is disconnects the old connection before it makes the new connection (break before make) or it connects the new connection before it disconnects the old (make before break).

Depending on which it is, there will be a delay added. for Break befor make you will add a delay time the enable . This will allow one side to disable first before the other side enables. For make befor break you will add a delay time to the disable wich means the other side enables before you disable the connected side.

So for the CBTLV3257 the enable and disable will happen at about the same time. There has been no delay time added.