Re: multiple copies of same app

If you are going to be managing the Apps; I would recommend building your app so that all your users can be in the same app; but they only see their own records.

You cannot make updates in one app and have them "flow through" to another app; so maintaining multiple "duplicate" applications will be arduous and time consuming.

Since you will be paying for the subscription; my recommendation here would be to create 1 app, and setup Users associated to Companies and permission those users for only records associated to that Company.  This is a very common usage case for QuickBase.