Now the processing profile explanation. They are currently a bit confusing and not consistent in terms of what type of thing they are. It really should be separated in to processing profile and output colour space.
But here's an explanation of what they currently are:
Standard - allows any creative processing to be done (contrast, saturation, curves and stuff like that), output in rec.709 colour space.
Tonemapped - Same as standard but applies a tonemapping curve so that highlights never ever clip (this limited by the camera unfortunately) - also output in rec709 space
sRGB - Does not allow any creative processing to be done (contrast, saturation, curves...), only exposure (linear) and white balance (white point adaptation) so the end result is a perfectly accurate output in the sRGB colour space
rec709 - same as sRGB, perfectly accurate, but this time the output is in rec709 colour space (basically the same thing)
linear - uses rec709/sRGB gamut, but no gamma curve. Not sure what the use is but I think @escho uses it. (?)
log profiles - Exact output, no creative processing, same as the previous two, except the output is in a log colour space which does allow processing
sRGB and rec709 are not very useful imo as they neither retain information for further grading like log does, nor does the image look nice because they lack a tonemapping curve.
This whole system will be reworked and more logical soon along with some very good improvements. I really want to get it done but I am busy in January sadly

Also @masc I noticed an issue, the curves and clarity adjustment do not get disabled in log and srgb/rec709 profiles which they should.