Outbox works amazing for finding replies. That takes very little effort when other clients broadcast their reply to *your outbox relays. The harder part is assembling a feed from your follows, not the replies. Almost all clients will do the broadcast correctly, only exceptions are allegedly damus apple and primal.
Amethyst in my experince tries to boil the ocean so much that it really has a hard time in general.. not due to outbox making notifs hard, but because it connects to 900 relays at startup so it really just shows whatever it can before the network stack dies.
If you want a lean way to check your replies and respond to them with an outbox broadcast try RelayTools-android or Jumble.
