Only if they are not connected, and each have a uniform horizontal cross section (or a similar overall shape)So if one section of ice is 1 metre thick, and another section 2 metres thick, does that mean the surface of the latter section is 10cm 'higher' than the first?
About 7/8ths of an iceberg is below the water line. This figure is approximate. Although icebergs are similar, not all are the same. Varying factors are iceberg density, water density etc. Keep in mind we are talking about an iceberg's mass. Due to irregular iceberg shapes, icebergs may have varying heights out of the water, but mass is relatively consistent.
So, the fraction of ice underwater, Vw/Vi, is given by the ratio of densities Rhoi/Rhow=0.87. Over 87% of an iceberg's volume (and mass) is underwater.