How much hold current is consumed when there is no load?
A stationary stepper motor supplied by DC is just a resistive load, so the maximum current which will be drawn is the driver's maximum output voltage divided by the resistance of the relevant coils.

When you're operating the motor at speed, changing coil current very quickly, you need a lot of voltage to impose the rapid changes of current.  For this reason, stepper motor drivers tend to have lots of voltage available, much more than you need to maintain a suitable holding current.

Because of this, the holding current is something which the driver has to control - it's not a matter of the motor 'drawing' it, so much as the driver imposing it.

It's going to be the case that a 1A motor has a higher resistance than a 2A motor, so if you had a constant voltage supply you'd see lower holding current when the 1A motor was connected without changing anything.  However, the mere fact that you've been told 'set the holding current lower' implies that actually you have a more sophisticated driver, which will have lots of excess voltage and will need to be told what a safe holding current is.