Hi Graham,
I'm assuming you are using software for backing tracks. You will not be able to use the Waves Multirack and your other audio software at the same time. The Multirack does not have any ability to play back audio tracks so you will need a secondary programs. It also will not run 3rd party effects plugins. The Multirack is designed to use as a stand alone software not in tandem with another audio software program running.

It would be more efficient to use the Waves plugins on inserts and the main out of your main audio software.
Tons pf people do this with Waves and other effects in a live environment. Cubase, Sonar , Ableton Live, Logic and reaper are all popular programs for doing this.
With the UFX you will be able to use the built in hardware effects on your output channels.
You can use Total FX to setup monitoring and routing independent of what your audio software can do. You also have the great added recording feature so you don't have to worry about doing this with your main software or with a different computer when you want to record your live show.

Thanks Chris

Hi Graham,
You main application uses and ASIO driver the same way the Multirack does so the latency would be no different.
There are some plugins though that do add their own latency into the signal. Many look ahead compressors, FFT EQ's and Convolution reverbs do add latency into the signal change. I do not use Studio One so not sure what it may do different than other hosts when processing a live input. As long as you are using audio plugins that do not have the extra buffer/latency added then the input to output latency would be the same as what you get with Multi-rack.
You can use GEQ or any other Waves or 3rd party effects chain you want to on the Main out and well as setting up effects chains on your live inputs and even backing tracks.You just need to make sure they do not add the extra buffer.

I know in Ableton Live, Cubase, Sonar and Reaper you can have your backing tracks tempo controlled and tempo locked to tempo based effects or visa versa. I don't know if this is possible in Studio One or not. Most likely there is some way to do it.

Ableton has some very slick abilities to assign backing tracks to MIDI triggers like MIDI Foot pedals.

Thanks Chris