傻帽一个 更注重于强调居首的 形容词“傻帽”，即 强调新来的小王“很傻” 一个傻帽 更注重于强调居首的 数量词“一个” 这种句子结构比较特殊 是：贬义形容词+数量词 （此处形容词 一般只有“傻帽”“笨蛋”“蠢货”等特定的几个贬义词）

if u put 一个 after a Noun(mostly sth negative, like an idiot or sth else) , u probably are making a judgement to sb to revile or devalue him. And u can finish your sentence then. But if you put 一个 before a Noun(either positive or negative both okay), u say it with or without emotion and judgement. In most cases, u have to go on to say sth about what happened to the Noun, and then your sentence is finished. EG, “你真是疯子一个。”（you are such a mad man.） “你是一个疯子/好人。”(you are a mad/good man.) "一个男人独自在街上走。"（a man was walking alone on the street.） Good luck with your learning.

suppose you quarrel with your friend, if you say"你就是笨蛋一个",maybe,it's only a joking,your friend is not angry with you.but if you said"你就是一个笨蛋"，maybe,your friend feel insulted. so, I think "笨蛋一个" has a little fun,it's informal and not serious,but,the meaning of "一个笨蛋" is totally opposite. furthermore,let's look at these two examples "我愿化作青烟一缕" and "我愿化作一缕青烟",you will feel the former is more beautiful and more romantic than the latter,this is a rhetoric of Chinese style, it appears in many chinese poem. I hope I can help you!

傻帽-------衣服、帽子不整齐，给人的感觉像傻子。

他们解释的都很不错了。。。我没啥加的了。。反正两个表达式其实都是可以的