Can you perform the first thing shown in that video, looking at a spot and dynamically spawning some object where you're looking with a keypress? If not, consider focusing only on that problem first.
yup i know how to do that
so you take the x,z position you'd place the object at, integer divide x and z by 10, then multiply x and z by 10, and just like that you're snapping to 10x10 grids.
IE: raypick returns coordinates 127,38. integer divide by 10 yields 12,3. multiply by 10 yields 120,30. so you picked 127,38, but snap to 120,30.
then its just setting the orientation (y rotation). axis aligning everything is one easy way to handle this. IE y rotation = 0, and make sure your models face the correct direction in your modeling software before export.
that's the general approach that first comes to mind.
this seems to be a good solution i'll try it as fast as possible