I used MidiSongToStyle only a few times and so I'm not really familiar with it. And because of that I will stick to what can be seen and done on keyboard.
Each of eight channels (Rhy1...Phr2) is totally independent from each other and so we need to set SFF parameters for each channels separately. Means, it's impossible to happen that we set BYPASS for all channels at once by coincidence -it simply can not happen.
However it did happened to me a few times, that I changed SFF settings on wrong channel. The reason was, because I wasn't paying attention on what "Target channel" is selected in SFF options.
Again, BYPASS setting is only needed for Rhy2 channel (because this channels only allows DrumKit voices). If DrumKit voice is also used in Rhy1, then obviously, BYPASS must be used on that channels as well.
On remaining channels DrumKit voices can not be selected and so BYPASS shouldn't be used on them. In short, BYPASS means: "ignore chord changes when playing" -that's not what we want for Bass (we want Bass to change notes according to chord that we're playing).
So shouldn't I use this option for the bass part when trying to correct the previous problem of drum sounds when changing chords?
I don't really understand... what option? Drums and Bass are two different/independent channels and each of them requires different SFF/NTT settings: Drums require BYPASS and Bass is usually set to MELODY.
Or I can do the same, but as you say, adjusting the excessive velocities later, in the keyboard editor? I don't know if by making these adjustments, in addition to the fact that the bass will sound less loud, I will be able to hear the phrases that were in the style before making the parameter change to "bypass" again.
Here I'm lost again... Why do you wish to change phrases to bypass again? I repeat: bypass is needed for drums only.
As I have mentioned, volume and velocity are not the same things, although both influence loudness. Velocity is, how hard you hit certain key on keyboard: if you hit key harder then it will sound louder (regardless of volume setting). In style (=midi) velocity is recorded/stored as a number between 1 (very gently) and 127 (very hard). In your styles (that you posted) all notes in all channels have velocities above 100 (many are 127) and so, even if you set volume relative low, it still sounds loud and harsh. Usually notes velocities (at playing) are somewhere between 40 and 60 -imagine that as gently playing piano. How would piano sound if you would smash the keys all the time? -and that's exactly what your style is doing.
I have no idea why you have such high velocities in your styles... I assume you changed something in MidiSongToStyle and so I recommend that you study settings there. But as style is now, the only solution is to reduce velocities on keyboard in StepEdit. And remember: you need to do that for each channel (in each variation) separately. You can try with some other (midi) software, though.
After velocities are corrected, you need to set volume of each channel (in each variation) by using Mixer. By doing that you balance the volume of each channel to get whole style in balance (so it sounds normal). And when you achieve that, style should have similar loudness as other preset styles.
And here's my personal opinion... You have chosen the wrong way to create styles. MidiSongToStyle doesn't mean "easy way to create styles". It requires complete style creation knowledge and even then there's no guarantee for success. Then you will install a bunch of editing tools on PC, trying to correct styles (with a lot of guessing and trying)... and end up with nothing really useful.
As strange as it might sound: The "easy way" is actually creating styles on keyboard.
Bogdan