The means of the two sentences is same, They can exchange for each other. The difference is the way you express .

洗完澡 means "finished the wash" 洗澡 means "wash or washing" “洗” is a verb,and in chinese,we don't have the same grammer to describe the action is done or doing like english "wash---washed---washing",so we used to add some special words or character to explain the verb, and "完" has the same function of "ed" when put it after a verb. such as :喝水(drink water) is the basic structure, 喝完水（drinked water） means I finished "drink water" 正在喝水 means I am drink-i-n-g water,here we add "正在" to describe the action is doing. I hope the answer can help u to understand it.

洗完澡 过去式past：我刚刚洗完澡 将来时future：我准备一会儿洗完澡去看望我的母亲 洗澡Can be a verb can also be a noun Chinese is a profound knowledge, you need to learn slowly, and don't worry, it's very interesting 希望对你有帮助

两个都可以