Hi tremainr
Thanks for your interest in Lumion.

1.
...do the wheels animate?
They rotate, but they do not turn in the direction the vehicle is heading.
2.
Did the newest version make it where the vehicle is able to follow the slope of the path and not "sink" into the terrain?
Yes, thats now possible, and easy to achieve.
3.
Is there a way to set up traffic simulations? such as where cars stop and go with out disappearing and looping? Or is that a task better for 3DS Max imported vehicles?
I guess that depends a little on the complexity of what is a traffic simulation

.
In any case, if the vehicle is in a
Mass Move path, it is currently not able to do a motion that is either a transition from travelling to stop or stop to travelling.
So yes, if that level of animation is required, then something like 3ds Max would be required.
4.
are the paths fixed to what they were in 3DS
You would need to specify the paths in Max, as it is an object that is animated, and that type of animation (apart from a stationery vehicle that's simply animating it's wheels) would need the path set in Max, for example slowing down or coming to a stop.
To put it another way, an object gets animated in Lumion. If that object is just the animated model then that is what will be controlled in Lumion. If the object contains a path from Max then both the model and it's path are part of the object so it wouldn't work to then try adding some other path in Lumion.
5.
and hope the paths lined up in a Lumion model
What is needed is to at least have a draft layout 'scene' in Max that will match that in Lumion, for example, the roads. That's easier to do if the roads are basically flat. If not, then the roads need to come from terrain and roading built elsewhere, or in Max before being finalised in Lumion, so that the vehicle paths are correct.
6.
I haven't found too many users of either software attempt much of this
Indeed, I'm also not aware of too many. Perhaps that's because the focus for Lumion is architectural visualization, and those added realisms all require further investment by architects in time and learning how to do, for what might not be a real requirement for communicating the design, concept and scene.
Don't forget that sometimes it's not what is done, its' what the user is given to see

for example a car might appear to turn off a road in to a parking lot, we can show the motion in to the parking lot without a lot of effort, and it's a given that the viewer will associate correctly where the car has come from, and add in the missing pieces to form the realisms needed.

Certainly 3DCordoba that specialise in visualizations and use Lumion do so such things, re your example 2 video. I would guess they use Max (but it could be Maya or one of the other high end 3D animation tools that can 'cleanly' export FBX or Collada animations.
7.
I would love to show cars and trucks turning into properties
Easy to do that now with either the
Advanced Move Effect (all recent versions of Lumion) or
Mass Move Effect (Lumion v6+).
8.
exporting it out to Lumion, and importing it with animations set to on, allow the user to define the path in Lumion and not preset in 3DS.
You need to consider the two basic forms of animation, as above. An object can be animated but static in position, so it's position can be controlled by a path in Lumion. Or, the object includes a path and so it (generally) has a fixed position in Lumion but still moves along a path.
9.
Is there a tutorial someone has made?
Not that I'm aware of, but if you find one please let us know.
We do of course have our own Video Tutorials (see link top of page) to cover Lumion features.