It differs a ton.
First off, think of the name "Yoko tomoe nage." Obviously it is going to the side. Well, tomoe nage is a ma sutemi waza, so despite the similarities in name, yoko tomoe nage has a lot more in common with yoko otoshi than it does with tomoe nage, IMO. If you throw yoko otoshi, then you have an advantage.
It's really difficult to explain techniques with just pure text. But look at this animation of yoko otoshi:
http://www.judoinfo.com/images/animations/blue/yokootoshi.gif
Now obviously the big difference is that in yoko tomoe nage, the left foot would be placed on uke's hip. This differs from regular tomoe nage because generally, the foot opposite the sleeve grip would be the one going to uke's hip (Of course there are variations, but this is generally how it's taught) and
because of that, tori's head has room to swing in the direction of the throw, and sometime - depending on a number of factors - right up close to uke's leg.
The kuzushi differs from both tomoe nage and yoko otoshi. It basically splits the difference. Yoko otoshi is virtually straight to the side, and tomoe nage is straight forward. Yoko tomoe nage is to uke's front right (or left) corner. What is unique is that due to tori's rotation as they swing to the ground, the final position is much like that of a traditional tomoe nage. That is to say that the kuzushi is to the front corner, but as tori swings into position, their head aligns with the original direction of kuzushi.
When I teach yoko tomoe nage I have tori start kuzushi and then put his foot into position, then I have them swing into position. I tell them to aim their head for uke's foot, and that usually ensures they swing into the correct position.