Basically, don’t bother, with Whispers, Bots just cannot reliably send whispers.
There is also nothing you can apply to to improve deliverilty, bot’s just can’t whisper. They may be able to reply to a whisper, so user sends the bot a whisper first and the bot replies.
But a bot cannot initate a “conversation” but it can (generally) paticipate in a user started “conversation”
Ideally, you need something like an External Portal protected by Twitch Auth, or an Extension, which is protected by Twitch Auth.
So the “secrets” are only visible to the right users in either.
An an “External portal” is easily convertable to Twitch Extension anyway.