Yes

You may pay online. 

A voucher is simply a payment option. 

But . . . WHY does it ask me for both?  Should I ignore that fact?  It doesn't make sense that it asked that - which is why I am asking this question. 

TurboTax always prints a Payment Voucher when you owe tax.   If you have requested a payment plan from the IRS, ignore the 1040-V.

You will get a letter from the IRS approving your Payment Plan.

Here's more info about the IRS Payment Plan.

SO . . . while I appreciate the reply, it is a tad late . . . I had to finish my taxes and so I already mailed the voucher with a check for a payment.   I assume that it will be applied to my tax debt; and then I assume the IRS will send me a letter . . . perhaps I assume too much.