Real wood ( Basswood ) .........why? Valances.....

You'd be far better off with a plantation shutter, perhaps? At least it has a far more finished appearance, there IS no valance.

I suppose you have a reason, but humidity, temperature will play a role too. Every room, what room etc?

I have no advice, I detest the dust catcher effect, cords, the stack is unattractive when raised, and there are so many other options, I never use them. . But that's me, not you : )

Unfortunately, I have shallow windows. I have learned a lot about blinds. Seems plastic wood blinds are more perfect looking and often have a one piece valence but I prefer real wood.

If you want real basswood, the ONLY wood used in wood blinds? Have it. Deal with the valance, or build your own, paint wall color and cover all the mechanism.. A shallow window doesn't dictate a blind: ) of any sort. And since you haven't posted pictures, said where they were going, shown the surrounding areas and your style? Nobody can advise other or better options.