Depends; hinges on vendor support in that specific model. If it works, it works seamlessly; OTOH, if this doesn't work well on that device, Bluetooth won't work

Depends; hinges on vendor support in that specific model. If it works, it works seamlessly; OTOH, if this doesn't work well on that device, Bluetooth won't work well, either. (Incidentally, sending files from featurephones to smartphones never failed me - BT seems to be well debugged there, as it's usually the only local networking option)