I can add some info on the pressure curves because i just tested them a bit... I noticed the following (just a simple patch routing pressure to the pitch):
1. when I applied max force on the keys, all pressure curves sounded the same in pitch... this tells me that none of the curves had lower dynamics.
2. when I applied medium force on the keys, the four pressure curves from 1 to 4 increased in pitch, telling me that the four curves are probably just upward logarithmic (curve 1 probably being linear, and the following being increasingly logarithmic).
This makes curve 4 most responsive on less pressure which is generally good for controlling low amounts in the ModMatrix, like for example vibrato amount, which usually is applied in very small amounts.
But for pressure modulation that have large amounts, curve 1 is more appropriate, as it will give you a feeling of better control of the pressure from low to high.
A trick to make the pressure more sensitive (greater reaction at lower pressure) with curve1 and modulations that require lower amounts (like vibrato), is to simply set a higher modulation amount in the ModMatrix... that means you'll be able to press too much vibrato in, but you'd have to press rather hard to get there... still it's a balance though... Personally I found that my prefered curve for pressure was Curve3... giving a medium logarithmic upward curve... with this I get a reasonably good pressure->vibrato feel, but still enough dynamics in the curve, that large amounts of modulation in other parameters have a reasonable resolution.