Each application has its own _data file which contains your shows, trials, classes and entries. This info is specific to the application. The myShare file contains your dogs, people and club and can be shared, hence the name, across all applications.
Both applications can link to the same myShare. You might want to store it in the RyKris folder above all the application folders to indicate it is used by more than one. If you do you will just need to remember to relink it when you upgrade because the upgrade by default will link to the myShare in the application data folder.
myNWT should be linked to myNWT_data and myOBT should be linked to myOBT_data.
I hope that helps.