DSP effects are processed in the order they are listed in DSP Studio. You can drag the effects to move them up and down.
There are two exceptions:
1) Output Format is always done first (the default ordering puts it at the top for clarity, but if you manually move it nothing changes)
2) Replay Gain is always done near the beginning because it applies at the file level, and doing it when other DSP effects are applied (just-in-time) doesn't make sense due to cross-fading, etc.
It is recommended that you leave Room Correction (or a Convolver if you use one) last since it changes phasing.
64bit floating point
bitdepth is used for all internal effects. VST plugins use 64bit when available and fall back to 32bit if the VST does not support 64bit.
All audio channels are passed to all audio effects. Media Center does not offer a way to push only specific channels through a VST. In other words, it is the VST's job to handle channel processing.