You can create a Custom Orientation from your Camera.
With that orientation in use, if you ShiftS snap the 3D Cursor to the camera, amd use it as your Transform Pivot Point, you can, for example, SZ scale an object up and down the camera's axis, and its appearance through the camera won't change.
If you want to create objects aligned to the camera, then on ShiftA creation, in the F9 'Adjust Last Operation' panel, change the creation orientation from 'World' to 'View', while looking through the camera. This can be set to be the default, in Main Header > Edit > Preferences :
If you have objects in scene, and you want to align them, along with their existing local axes, to the camera,then, having created the Camera Custom Orientation, use Header > Object > Transform > 'Align to Transform Orientation'.
If you want to leave meshes in place, but align the object's local axes to the camera, then, in Object Mode, you can use Header > Options > 'Affect only Origins' , and align only the axes to the camera, using the above method.