Titus Canyon Road is an awesome drive, but it requires at least high clearance (sometimes 4x4) and is a dirt road with some steep narrow rutted sections. And as you said it's one-way so you can't change your mind and turn back. It isn't really suited for most rental cars (even rental SUVs technically can't be driven off paved roads), and isn't something I'd recommend for a first-time trip to DV, especially not if driving in the same day from Sedona. You can park at the western edge of the narrows and walk in to see the most spectacular part.

If you're coming straight from Sedona and leave reasonably early, come in via Pahrump and you should be able to stop at Dante's View and Zabriskie Point on the way in (and if not you can hit them on the way back to Vegas). The next 1 or 2 full days can be spent doing any number of short/medium hikes along Badwater Road, Titus, Stovepipe Wells area (including dunes and Mosaic Canyon), and maybe Ubehebe Crater. Don't feel you have to do it all, because if you're like us you'll know you want to come back someday anyway :-)