If it is going to be painted, or for under a second layer of planking, I use Durham's Rock Hard from the hardware store. cheap and easy to work with. I don't find any odor problems. Dries hard and is easily sanded. It is a powder that is mixed with water and as such I am careful not to inhale it before it is mixed with water. I mix it to the consistency of peanut butter and sand it the next day.
Not a good option if not painted. Then I try to find a product like minwax colored wood filler.
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RossR's post in Wood filler recommendations was marked as the answer