IMo, hard to tell. Biggest sign is if the tires are wearing uneven. If axles are out of alignment, you will see significant wear within a few hundred miles. I wouldn't worry about not being centered in the fender well. If axle moved that much, you would see frame damage, loose/missing mounting bolts, etc. My guess is that fender has either been tweeked, replaced, or never was centered.

If a torsion axle is bent, typically, it is almost undetectable with a tape measure. You will see abnormal tire wear as the primary indicator.