I want to be able to reliably move objects in Photoshop with the arrow keys by 1px, regardless of zoom. When the document is not at scale, the arrow keys randomly move objects by either 2px or 3px (alternating between them whilst zoom remains the same). Can someone help me with this? Thanks.
To my knowledge you can't change the default nudging behavior.
What you can do is record 4 actions: for moving a layer in 4 directions and assign them to hotkeys.
However another problem is that it's impossible to reassign some hotkeys in Photoshop, including the arrow keys, so you won't be able to assign the actions to arrow keys. A solution to this would be using a 3rd party remapping tool (like AHK on Windows or Keyboard Maestro on Mac) to remap keys, for example remapping Win+Arrows to whatever F-keys that are used for move actions.