Here is the word on the Z1000 and the PH180 power brick as I understand it and in my personal experiences with the MTH 100 watt power brick:
The PH180 circuit breakers are of the fast acting type and previous versions of this power brick needed no external circuit breakers. That has been the consensus on this site for several years. The newest version is unknown to me, as it has just become available after several years on back-order.
The 100 watt power bricks (as used as part of the Z1000) that I have (bought new about 3 or so years ago) ABSOLUTELY needed auxiliary circuit breakers. I have them as part of my MTH DCS/TIU/AIU digital control system. Any short (a derailment) would not trip them and instead pop the fuse inside the TIU. But the TIU is screwed to the layout and wired in. It takes a dozen or so tiny screws to get access to the fuses after physically removing the TIU from the system wiring and its mounting point. The 20 AMP(!!) TIU fuse would blow before the100 watt power brick circuit breaker would trip. After about half a dozen of these laborious fuse replacements, I did too things. (I have two of these and both acted the same)
I found a 7 AMP aviation circuit breaker that was about as fast acting as possible (magnetic rather than heat activated). According to the curves in its specifications, it would trip in less than a second, protecting the TIU fuse. To be doubly safe I wired the TIU in the "Passive Mode" which relieves the TIU of providing power to the trains and the TIU only provides communications with the trains. The only down side is you loose the emergency stop feature of the remote so I bought a remote lamp controller from the hardware store for such emergencies. I have not replaced a fuse since this change. The breaker trips fast and reliably. Those breakers are hard to find and expensive. The one I found was used from an Aviation salvage company. Even then it was not cheap. not all magnetically trigger circuit breaker work at the same speed. You have to research them and find the virtually zero delay type.
Now, maybe newer power bricks use different circuit breakers...I don't know but I doubt it as the fast breakers are more expensive, it seems.
LDBennett