Yep! All of the above. A failing PSU can manifest into many symptoms, some that don't even appear to be power related. While it is rare these days for a failed PSU to take out connected devices, it can happen.
The power supply is already making a very loud noise and I'm not sure if it is the fan motor or the transformer.
If the noise is the fan, the pitch of the sound the fan makes will change as the rotation speed of the fan changes. So if you can see the fan, you can carefully press a wooden glue/Popsicle stick on the center hub of the fan to momentarily change the rotation speed. If the noise pitch does not change when you press on the center hub and slow down the rotation speed, then something else is making the noise.
If a transformer plate or winding, or a coil winding is making the sound, the pitch of that typically changes as the load on the supply changes - though the sound might change as the temperature within the PSU changes too. Transformer and coil noise don't always indicate the component is about to fail. Those plates and windings want to vibrate naturally which is why they typically are glued/sealed in some sort of epoxy resins. But an incomplete seal or some other physical abuse can break that seal, causing them to vibrate and start whining. But they still can continue to work just fine for years - if the user (or their dogs) can put up with it.
If you are getting unexplained and unexpected system lock-ups, shutdowns, or reboots, I would suspect the PSU.
Unfortunately, there is no way a normal user can thoroughly or conclusively test a PSU. That takes an oscilloscope or power supply analyzer, and a properly trained tech. So the next best thing is to swap in a known good PSU.
