He may be tamer sexually because he is sensitive and doesn't want his sexual needs to dominate. Betas may be gentle, not rough lovers. They try to intuit your needs and seek to put yours ahead of theirs, which Alphas definitely don't.
There are many healthy relationships with female breadwinners where the men have their own ambitions and drive. I believe there is a new type of male/female relationship forming in our culture not defined by who is more dominant and successful.