The mixer window gives you access to every effect, plus overall level, for each track. It gives you real-time tweaking control over each track.
Series and Parallel:
"In a typical serial configuration, the signal travels from the output of one effect directly to the input of the next. In a serial setup, all of the faders will be set to zero except for the final fader, which will be set to 100%. All of the source selection inputs will be set 100% from the previous effect, 0% from the dry source.
In a typical parallel configuration, the signal for each of the effects is dry (100% source, 0% previous), and the outputs of the effects are mixed in equal parts to the output of the FX Mixer. If there are three effects in the current effects rack, each fader will default to 33%. If there are four effects, each fader will default to 25%, etc. This allows effects to be used that are not chained."