‘Boku’ and ‘Ore’ are almost exclusively used by men. You often hear young boys refer to themselves as ‘boku’ as well as adult men. ‘Ore’ is much more masculine and strong.
Typically, it’s more proper for men to use ‘Boku’ or ‘Watashi’ when referring to themselves at work or in polite situations. ‘Ore’ is heard more commonly in private situations amongst friends or in casual situations.
As you mentioned in your question, ‘Boku’ is often used by female artists in their songs. There are a number of possible reasons why artists do this. For example, it can be because the female artist wants to portray the male perspective, or to imply strength, or simply because it sounds better in the song lyrically compared to ‘Watashi’ or some other variant of ‘I.’
‘Watashi’ is the standard way to say ‘I’ and can be used by both men and women. ‘Watakushi’ is a slightly more polite way of saying ‘Watashi.’
‘Atashi’ is a feminine way of saying ‘I’ used almost exclusively by women.
‘Anata’ is often taught as the standard way of saying ‘you’ in Japanese but you should be careful with it’s usage. Generally speaking, ‘Anata’ is only appropriate to say to people who are the same age as you or younger. To show respect, it’s more common to refer to the person by their name (typically their last name+san).
‘Kimi’ is also usually used by someone of higher rank. So using ‘kimi’ can often sound condescending. For example, a teacher may refer to a student as ‘kimi’ but it’s rude for a student to refer to their teacher as ‘kimi.’ You often hear people refer to family members as ‘kimi’ but some people dislike being called that so be careful.
‘Omae’ is a very rough way of saying you. It’s very masculine, like ‘Ore’ and that’s why it’s often seen as being impolite. Although it’s common to hear husbands refer to their wives as ‘omae,’ it’s case-by-case since many women nowadays don’t appreciate being referred to by that term.
Again, for polite situations, the safest and most common way to refer to someone is to call them by their last name + san. In casual situations, it’s most common to refer to people by their nickname or whatever name they like to be called.
