Associating Specific Contacts to Individual Opp

Currently, when we create an opportunity all contacts are shown under the relationships tab.  We don't attach them, but I am wanting to "Attach" a contact or multiple contacts to an opportunity if they are associated instead of every contact showing on every opportunity.

I think i saw a way to change the way contacts appear on opportunities (or maybe it was for proposals so all contacts don't appear?), but i cant remember where.  I also want to know potential ramifications that this may cause if we de-associate EVERY contact.  Will this remove all contacts from previous opportunities if we change this? or will it just pick up from when the change was made.  I would like this to be a going forward change that will not affect anything previously created, but change the way we will create opps moving forward.