Unfortunately the only way to keep todays standard grade lumber straight is to keep it banded. Once unbanded, good framers quickly install what they need and leave the rest undisturbed in the bunk. Nested tight in the bunk help keeps it straight, and slows
loss. That's especially true here in the arid western U.S.
You have a nick neat pile of lumber there, nicely stickered. Good work. Fortunately you have picked good stock to rip, that is relatively knot free. Unfortunately, if the grain isn't dead straight and without internal stress, it will start warping twisting bowing as it dries. Knots are what's a real killer. Some warpage is no big deal.
I have some 1x3 rafters so twisted they are vertical up at the roof ring, and have a full 45 degree twist down at the wall. Unsighly, but they are fine as the snow load here is pretty marginal. Up at a ski area in the Rockies would be a different deal. I'd want them real straight up there.
Sorry, can't advise about stain and seal in one. Never done it.
Keep up the good work.