The geometry node setup can be quite demanding from your computer. If you can't use it right, try to reduce some resolution settings that can make it more friendly for your computer.

Whatever you desire! The geometry node sequence is set up in a way where scale & mesh resolution doesn't matter. So it should take care of any object input.

Once you have your final object scale, make sure to apply the scale transform. That will make the material acquire the right dimensions and fit your object nicely.