I think the 2Kw would be too small for a trailer in the winter. 5Kw is ok, but the 8Kw would be better. Or if you have a very large trailer, even 2 of the 5Kw version would be good.
No, there is not a smell at all. In one of the videos in the series, he goes over how little emissions these heaters put out.
The fuel consumption is also covered in one of the videos, as is repair and maintenance. VERY informative series!!
These are a chinese knock off of the Espar or Eberspaecher heaters, which are $1000 or more.