HMC
How one should handle their security and system setup absolutely depends on the jurisdiction(s) in question.
Biometrics are security theater in basically every jurisdiction as law enforcement, much less other threat actors that might detain you, will force your finger on the phone or hold it up to your face.
In most US states you have 5th Amendment protection against being forced to provide a password/pin yo unlock a device. Refusal to provide that information can't even be mentioned in front of the jury. Note that this isn't all states and a case has yet to make its way to the US Supreme Court for a definitive answer.
If you are crossing the US border and are a US citizen, the US governments ability to examine your electronics, much less unlock them, is sharply limited. The most they could do (generally speaking) is seize the device but even that is unlikely.
If you aren't a US citizen then they absolutely can force you to unlock the device and even perform a full forensic extraction if you want to enter the US.
Other jurisdictions have their own quarks and rules. Always be careful when traveling and if you have questions talk to a legal professional in advance of visiting the jurisdiction.
If US customs are your concern, you are generally better off encrypting the data, uploading that encrypted data to Proton Drive or the like, crossing the border with a clean phone, buying a pixel in the us (can be done with cash at basically any electronics store), loading GOS onto it, and downloading the encrypted data via said device.
None of this really gets to my point in this thread though.
Once you become a person of interest in an investigation, law enforcement us going to ask to view your phone. Assuming the jurisdiction in question allows you to refuse, the simple fact that you have refused is going to make you a bigger focus in the investigation.
Getting a warrant to seize a phone is generally fairly trivial, and once law enforcement has that they will seize it and try for a full extraction.
If you provide a duress pin and wipe the device then you are very likely to be found guilty of destruction of evidence. In some jurisdictions, the mere fact that you have destroyed evidence means that the court gets to assume that the destroyed evidence is basically as bad for you as it could possibly be.
So, assuming that your phone is secured with a strong password/phrase, the usage of a duress pin is often worse than doing nothing.
Your phone is seized and its encryption won't be broken in your lifetime. In the US the inability of law enforcement to crack your device can't be used in trial (generally speaking).
If the use of a duress pin could be concealed and it only wiped specific data (I.e. a private space) then when law enforcement asks for access you can freely provide it, confident in the knowledge that your phone won't incriminate you. Instead of evidence against you, this makes your phone evidence in your favor at trial.
Where you get into more of a gray area is writing down the duress pin somewhere it is liable to be found, refusing to help law enforcement get access to your phone, and then waiting for them to try that written passcode on their own initiative. Again, consult a legal professional before doing something like this.
Personally? When I travel I use a device specific to that trip. It is factory reset before the trip, loaded with only what is needed for the trip, and my assumption is that everything on that device is compromised by the government of wherever I go. Upon return the device is factory reset again. If I visited some countries, most notably the PRC, that device is then sold to someone else.
If you are crossing a border with GOS on your phone and it is examined at all you will become a person of interest to that jurisdiction. Period. If you want to avoid that, buy an iPhone to use for traveling and don't do anything dubious on that device.