I’ve found a way to answer part of my question and I thought it could be interresting to share.
I’ve set up a effect of +1 dB and I took SPAN VST to help me out what was the highest peak. Here’s a very approximated calculus because each WET value are about +/-5.00, which is big, but it can give an idea of how to translate dB to %. It seems to respond to more to a logarithmic curve than a linear one…
Here’s what we got :
Hope it helps you too!
Thanks for everything! 