You can set what note the pads are triggering via the module, at least on a DM-5 you can, I've done it. I noticed when I first used my e-kit with EZD the ride was triggered by the farthest cymbal pad on the left (normally a crash), so all I did was switch the cables from the pads to the module and that worked. However, the toms were not right, they were triggering cymbals instead of toms so I had to go into the module's settings for all three tom slots and change the note they trigger. About 2 minutes of fiddling around in the menus and I had a fully functioning kit.
As far as the map goes...it just makes everything fall into where it should be, visually. Unless you want to always go "does D2 have a china or a tom flam on it...". With a map it is labeled as to what that note triggers. This is especially handy when programming by hand or when editing MIDI you've recorded from an e-kit. Speaking of which, I started working on a map for the DFH EZX. The map you can get from ToonTrack is only for EZD, so a LOT of the things that DFH offers (a lot more cymbals, crescendos, etc.) are not on that map, obviously. So I went through and started labeling all the notes that triggered something, and what it was. For cymbals I put which position they were in, and if they were left or right panning. Then everything is broken up into groups. You have all your hats, kick l/r, snare l/r, toms l/r then all the cymbals, including l/r for each*. Then I have a group of all the flams for snare and toms, then crescendos and mutes. Really helps and ends up looking a lot more like the DFHS map, which always was easy to use and figure out.
~e.a
* - I do the "left and right" hits by basically finding the two notes that trigger the same exact cymbal the same way. Making a "left" and a "right" trigger makes it easier to make your own crescendos, and variations with velocities on embellishments involving neat cymbal work. The EZD VST still triggers random samples no matter which note out of the two get played.
thanks 
