[el Daniel]

The bus outputs are 24 bits dithered when the dithered mixer is used, so you don't have to insert any dithering plugin when bouncing to track in a 24 bits session.

The master faders are always present just before the bus output, it doesn't matter if you have created the master or not, it's the last gain stage in the 48 bits enviroment just before dithering and truncation to 24 bits at the bus output. If it is not created in your session it is there anyway at unity gain.
You have to have in account that the inserts at the masters faders are post fader and post dithering and truncation so the signal arriving to these inserts is the 24bit dithered signal.

Then, if your session is 16 bits and you want to bounce to track, you have to assing the outputs of your tracks to a pair of busses, then create a master fader for these busses and insert a 16 bits dithering plugin in the master fader(i.e: all your tracks outputs -> bus 1-2, master fader output -> bus 1-2, 16 bits dithering plugin in one of the master fader inserts, recording track input -> bus 1-2).

Therefore, your mix is routed to the bus in a 48 bits wordlength, it is summed at 48 bits, then is dithered and truncated to 24 bits, it goes to the 16 bits dither plugin inserted in the master fader, and the 16 bits dithered signal gets in the recording track.

I hope all this makes sense.

Daniel.