Hey I have that mystery white flower blooming in my garden too! I received it as a gift from a hillside native plant gardener and never did know the name. So I am working hard to find out for sure what it is called. So far my best guess is that we both have Oconee Bells or Diapensiaceae. The flowers emerge before the foliage followed by rounded, glossy green leaves. It is difficult to propagate but dividing the tubers  in the spring after it blooms is more successful than trying to grow this wild flower from seed. I will edit this answer if after hearing from some experts I can determine with more certainty the name of this lovely low growing plant. Now for the smoke tree I would not worry yet if there are no leaves on the plant. Cotinus coggyria or smoke tree is notorious for staying dormant until late in the spring.  Keep growing, Marianne Binetti