A long time ago, when learning DAW recording I seem to recall that the "output" setting of each channel should be set to Master, even though there will be bus-sends from these same channels, for fx, etc. But really what about grouping - vocals, drums,,,to a bus just for level control purposes for example, should that be done via the output or a send to that bus. Thanks CS

Tracks go to the master. Sends go to buses. Buses go to the master. The master goes to the main outs.

The grouping of groups is easiest done with a bus. you don't want to use more than one output. Or outputs should be 1 and 2 of your sound card. your outputs are your sound card outputs

I rarely output tracks directly to the master bus, instead outputting to "sub-busses" like vocals, guitars, etc, all of which route to the master bus.   And the master bus routes to the mains.   That way each sub-group can be adjusted as a whole, not to mention group compression and/or EQ on drums, etc for a little extra "glue".
 

Also to what CJ is speaking to - tracks can be sent to a bus via output or send. The bus in turn will likely go to the master out.

I group (output) vox or guitars or drums, etc to their own bus to control the overall sound in one place most of the time.

I use track sends to a bus primarily for using efx.

All of your tracks (and busses) MUST end up at the master bus, but often the route taken can vary from track to track.

For instance, I might route my drum tracks to a drum bus, but I might also route my toms to a tom bus, which in turn gets routed to the drums bus.

This is set via the tracks OUTPUT control - don't confuse this with the SEND

A SEND is used to take a copy of an existing signal, route it to a bus where further processing is applied to it, e.g. a reverb or delay. This signal is then blended in with the raw tracks

Sane with vocals. I might route my lead vocal tracks to a vocal bus, then route my backup vox to another vox backup bus. This bus then could get routed to either the main vocal bus or straight to the master, depending on what I want to do with the combined tracks.

Just make sure nothing is routed directly to your interface/soundcard.

As to stevec's point -that is the scenario I was imagining, which makes sense to me  

silvercn - right, stevec's suggested routing is a preferred technique.