If you e-file and owe the IRS -- and you've elected to pay by check -- then you'll mail IRS the check along with the payment voucher (1040-V) which will be included in your tax file and can be printed out. It's just a small slip -- about 1/4 of a page -- like any other bill you might pay.
When you e-file, you won't need to mail in a hard copy of the return or any additional forms or schedules unless TurboTax specifically instructs you to do so. On occasion, the IRS may require a particular form or schedule to be mailed in, but TurboTax will tell you if that specifically applies to you.