If you are using a stereo mixer without ToneMatch, by panning vocals all to the same side you can take advantage of the S1 Vocal ToneMatch preset. Should the other channels in the outboard mixer be guitars, those can be panned / routed to the other S1 channel utilizing the guitar Tonematch.
If there is a mixture of instruments it still might be preferable to pan opposite of the vocals, but chose to not use the preset for that channel.
Use of ToneMatch presets is a choice. If you like the sound fine, if not switch it off.
Like others have said, it is best to start with all EQ set Flat, or knobs centered. Set levels, then utilize EQ controls on the outboard mixer.
Effects? Same as EQ, chose which device you want to use, and turn effects off on the other.
By utilizing the Vocal ToneMatch you have effectively put a very sophisticated EQ curve in the signal chain that enhances vocal clarity in a way that can't be done with a simple two or three band Channel EQ.