It looks like the coaster building will be like I thought (but feel free to correct me, Mr. B):
What I assume is that all paths will be pre-placed, and that some flatrides will be pre-chosen as well. When it comes to coaster building, there will be fenced in areas where you can build your coasters, so it will be freeform inside of the fence. I would assume that you pick the kind of coaster, and it would autofill the queue path, and you just drop down how long you want the station platform, and then build away. That seems the most logical to me on a console.