What options do I have for the Login screen?

The login screen looks the same for both B2B and B2C except for two things:
1) In a B2B environment you can choose to not allow customers to self sign up. This option can be found in the site settings> general info> Site Basics "Allow self-signup." If they don't check that option the "create account" option will not display on the login screen. 
2) If the account is set to use a universal login, both the lost password and the create account options are removed. That option is in the same place as the option above. Both are part of the site basics.
Click here for the chapter that explains self sign up and universal login in greater depth.