Seeing as if 4D

[anagogy]

Otherwise, according to Ra its incarnations are unconsciously chosen.

Well, in the quote I posted above, Ra said that Gandalf himself can choose harvest, OR choose reincarnation again with his loved ones. Would that mean Gandalf is... mid third - fourth density harvestable?

To my way of thinking "harvestability" would imply that the energy had become sustained for the most part.  So if you were 3rd density harvestable, you would have to have sustained self awareness (like your way of looking at the world had shifted fundamentally and become part of your identity).  Same goes for being 4th density harvestable, polarization would presume you have more or less turned on green ray permanently or at least, consistently enough to warrant incarnation in that realm.  I have no doubt we have moments of flashing into other rays -- indigo ray, blue ray, violet ray etc.  But the energy isn't "seated".  In the same way, I think a second density being could be 3rd density harvestable, and have a small degree of activation in green ray due to efficient use of catalyst, but it isn't sustained.  Otherwise it would be possible to skip densities.  As far as I'm aware, that isn't possible, but that is another question I wish they would have asked.