Not all mature bucks look the same. Some are short and squatty bodied while others are long/lanky bodied. Color daytime pics are the best for aging. So you can see details/shape on the head, face, ears, neckline, body lines, depth of chest, width of brisket in-between front shoulders, belly, flank, stained hocks, calloused knees, how they sit on their hooves, backline, rump area, etc are all part of aging a deer on the hoof.
I would call that buck in the second set of pics a 4 yr old in most of the pics except the one profile he has the head/jaw//neck of an early season 5 yr old. He just does not have the depth or width of the brisket in the front shoulder to be a 5 yr old to me. The more pics and angles you have to judge by the better you can get.