Maps and layouts are automatically assigned only with the default Finale instruments. Because VDL is a third party library it is up to the user to set those. if you are using a TWS template then it should only require you to check and verify that these are correct. Understand that if you change instruments, say from Snareline Manual to Snare Solo Kevlar, you would need to match the maps and layouts. This is also true when changing any non-pitched percussion instrument.
As for transpositions, if you add a new instrument staff (for example when you are creating a score) and use the Add Instrument button in Score Manager, transpositions will need to be adjusted. Once the staff is set up then when using the Instrument Change Utility it is not necessary to change the transposition for the pitched instrument.
Hope this clears things up.
iMac i7, OS 10.8, 10.9, W7
VDL2.5.5, Finale 2010-14
Kontakt 4-5, various other soft synths