Is the difference in the size of these holes
normal and ok?
These are the T282 B and T270 B spindle arms.
Is the thinner one worn and not usable?
The arm on the right is missing the bushing. If its worn oversize, then the bushing will be loose and you may need to replace the arm or maybe just Loctite the bushing.
The thin one does not look right at all. /Could be the angle of the shot but the hole looks way big and the arm looks a lot heaver then the other one.