Q1. When I share privately and get the link to share with those that I want to share with, do I need to provide a trigger image or does it automatically come up like on the ones publicly shared?
Q2. Is there a maximum number of users that I can share the link to?
Q3. Does each different aura have its own link, or does the link only need to be shared once and it works for all that I create?
And here are the answers!
A1. When someone follows a subscription link, the private Auras you share with them will appear in their Auras list in same way public ones do - so yes they'll get to see the trigger image.
A2. There is no limit whatsoever to the number of people that can activate a subscription link.
A3. Your subscription link is unique to your account's private Auras, so once followed users will be able to activate all the private Auras you have created - so you'll just need to share it the once.