If you do not want your Launchpad buttons triggering your software instruments (e.g. Drum Rack) at maximum velocity (127), Ableton includes a handy plug-in called 'Velocity' which is ideal for limiting the velocity to your ideal specification.
Select the MIDI track you want to limit in Live, then go to MIDI Effects > Velocity in the 'Live Devices' section on the left of the screen.
In the plug-in section, simply adjust the 'Out Hi' setting to whatever you would like to maximum input velocity for that track to be.
TIP : You can raise the 'Random' parameter in the velocity plug-in to give your playing more of an organic feel.