Even the term "driftwood" is open to different definitions so what works for one may be different for another. One big point is the water we put it in as well as the wood. A wood put in water with little buffering is far more prone to changing things than the same wood in water with lots of buffering so the answer will vary.
But some basics that seem to work for most cases are simple enough. In my view, wood is made of three things, the wet stuff like sap, tannin, moisture or whatever we call it, the hard cellulose that makes up much of the rest and then there is always the question of what foreign items may be on/in the wood. Roots are more likely to have dirt than other wood might but then dirt is not really much concern in a planted tank!
Since it is nearly impossible to ID most truly dry driftwood, I go this way.
Dry wood avoids most of the question of the moisture, tannins, etc., so I go for only the truly dry stuff. The hard stuff is rarely/never a problem but the wet stuff can drive you crazy for months.
I wash it off and do a bleach soak to clear all the other questions about what might be picked up by the wood while it has been out wandering around.
For hard wood/softwood, I don't care as long as it is totally dry and hard enough to touch to make it seem it will last long enough for my use. Obviously a wood like bamboo will go to mush quicker than something like oak. But if it feels good, I use it.