Does the smoke hang around the car in sort of a cloud? Could the smoke have a slight blue tinge to it? The 3S-FE engine in your Rav-4 is quite similar structurally to the 5S-FE used in the Camary. The 5S-FE had a problem where oil would leak past the valve guide seals on top of the valve or into the cylinder. When the engine would be started after an overnight rest a cloud of smoke would appear. This might not happen every cold start but occurred sporadically. I suspect only one or two valve seals were leaking and that valve had to be held open on shut down for the oil level to get high enough to leak past the seal. My understanding is that the oil consumption was not noticeable but the annoyance of producing a cloud every so often was the concern.
If this is truely oil burning off, there is a slight chance that it would affect the catalytic converter but I have not read of any cases where this was proven. The valve seals can be replaced without removing the head but it does require taking the cam shafts off and releasing the valve springs to get to the seal. At this point you might as well install a new timing belt, water pump, and kit, and check the valve clearances.
Hope this helps.