[brackets mean hold down the button]
The TB-3 touchscreen doesn't respond to velocity from the keypad. However, velocity values over 100 trigger the accent function when sent from an external controller.
User patches U01-U15 cannot be selected with program change, only with the value knob. For live performance, the only way to select user patches without touching the front panel is by using the patch data sysex command.
Pad Z functions as a switch, not as aftertouch per se, and should be assigned to parameters with only two values. For example, you can set Pad Z to distortion or noise switch and it will stay active as long as you hold keypad down. When you release, the sound will switch off. If it doesn't seem to work, your sensitivity might be set too low, so go into global settings and increase the sensitivity.
The difference between pattern transpose and pattern pitch shift is that pattern pitch shift changes the notes of the pattern while transpose changes the base key or starting root note of the pattern without changing its notes. Also, with pattern pitch shift, when the notes are pitch shifted beyond the upper and lower limit of the note range, they cannot be shifted back to their original pitch. Essentially pitch shift is destructive (changing the pattern's notes) while transpose is nondestructive (saving a key signature on which to start).