As far as using that huge tree for boards, you may be disappointed in the lumber.
Around here (Wisconsin) Poplar is known for warping and twisting. Even if piled and stripped correctly and appearing to cure straight, the lumber will curl as you unpile it. It also is very susceptible to rot and decay if it is allowed to get wet.
In addition, limbs are even worse, as there are “corrective” forces present in a limb as it tries to support its horizontal weight while growing. Even a leaning tree has these forces present, and they appear as soon as they are sawed into a board. When sawed, the lumber still remembers those forces and they influence the straightness when those forces are released in sawing.
That said, the interior studs of my 1976 house are home-sawed poplar and they are as tough as any wood out there. Unbreakable and hold a nail like there is a nut on the backside. A poplar (aspen) 2X4 used as a lever almost can’t be broken.
But the builder had to cut and splint many of them to straighten them. Hardly worth the effort.
If they are to be used as sheeting, one option is to nail them up tight, green and directly off the mill, thus holding them straight while they dry and keeping them straight for “the duration.” Hopefully their shrinkage can be tolerated. Shrinkage is worst in their width, but almost negligible in their length.