Kathleen,
I would subscribe to an "add to the model only" method and not delete anything--at least until you become familiar with the various applications and what fields they are using. Your concern is valid and you don't want to paint yourself into a corner unnecessarily!
You can hide fields by unchecking them in the layer properties within ArcMap. That may or may not have consequences with the apps you want to use, however.
As long as you do not mind having an empty field in your data then you would be better off leaving the unused fields. It is always easier to add fields in before you begin to use the data.