The stuff you want is all in the trichomes on the outside of the plant. Once you freeze the fresh material, ice crystals will have ruptured the cell walls, so it's important to not let it thaw before extraction, or you will be extracting material from inside the cells.
The quality is typically good, when done properly, typically aromatic and closer to pull and snap than shatter.
Yield is about proportional given the extra bulk of the water. You just have to do more runs to get it.