Ok, so if I understand correctly, the general idea is to setup your inbox/outbox relays plus some other relays based on the client and on what you want to do with it (social, chat, etc...). So in my example above I should only set inbox/outbox relays plus some other "read" relays for everything else (whether they are called app relays, search relays or something else doesn't matter). 

 I don't think I can offer general advice, because each client will behave differently. Clients should probably guide you better, or set up some nice defaults for you. 

 Oh, last question: let's say I change inbox/outbox relays, but I don't want to "lose" events, would you say rebroadcasting everything I have written to the new ones is the correct thing to do? How would you manage this situation? 

 Yes, rebroadcasting is the correct thing to do.