[Ben Jenssen]

As to the "threshold question" (which was never a question, really?), the threshold is a parameter on dynamic plugins like compressors, gates, and such. It's simply the point you want the effect to start. If you set a compressor threshold to -0, any signal over -0 will be compressed.

But remember, with "analog emulation" in plugins today, a plugin might add a "flavour" of sound even with settings at zero. You might hear a difference just by driving its input level.

So, test them out, driving them hot or not. Often there's a "sweet spot" where you find a plugin creates that little extra. Like a opto compressor on vocals typcally around 2-4db gain reduction.