IF you find a tow driver to tow a truck with trailer attached then u lucked out. Most will not even try, or most will say "insurance something so I can't".
A 5th wheeler is a different legal animal. In most States you can tow a 5th and attach a trailer to the 5th wheeler trailer, but if talking 5th wheelers then usually talking very big trailers to begin with.
Usually you will need trailer towed behind the flatbed or by another vehicle entirely. Don't count on the driver pulling your rig with a little tow truck.
The ability of the tow truck is not nearly important as what the driver is willing to do. Yes, a diesel can pull your rig easy, but no, the driver will probably not do both truck n trailer.