Let’s assume you have a trunk link between SW1 and SW2. If you configure the port on SW1 as a trunk and you also configure the
switchport nonegotiate command, the result is you will have a trunk port on this end that will not send out DTP messages.
In order to get this trunk link to function, you must configure the port on SW2 manually as a trunk as well. If you don’t, it will try to listen for DTP messages, it will hear none, and it will remain in the default state of access and the link will not function.
If you configure SW2 as a trunk, then the link will come up. At this point it doesn’t matter if SW2 is sending DTP messages, the result will be the same. But it is good practice to disable it, because at some point in the future, when you disconnect the switches and connect them in a different topology, the state of DTP may affect what the link ends up becoming, possibly causing undesired behaviour.
I hope this has been helpful!