You will have an account. If others use your computer, they too will have an account. Without knowing your password your information will not be used by others. If you have programs, they can be shared by all through the use of permissions.
I think the best way to see the effects of your choice, is to make another user account. Then you can see exactly what can be accessed.
I want to give you all the help that you need. If you set up a "test" user account and there are somethings that you do not like, give me specifics and I will help.
My question to you, is. If I have a file in my user account, and you have your own user account, how do you access my files?