For the pots, you should wait until the soil is almost dry (easier but not necessary), palm the top of the soil with the stem going between your fingers. Then just turn the plant upside-down. Carefully pull off the old pot, tapping lightly if needed to get it to budge.

About the height, there are some threads around about the "stretch"... but it depends on strain also. If you have height issues, look into LST and SCROG, they worked great for me... and you don't have to limit the size of your plants according to height.