Android notification channels: keeping critical alerts audible while silencing routine ones

I manage an Android app targeting API 26+ that posts several notification types: time-critical alerts (e.g., security events) and routine updates (e.g., daily summaries). I want users to be able to silence the routine updates without losing the critical alerts, and I want the defaults to be sensible so users do not have to configure everything manually.

I have created separate notification channels per category, but the behavior I see is unclear in two areas. First, when a channel's importance is set to high, the system plays sound and may peek on screen, but I am unsure how that interacts with Do Not Disturb: does a high-importance channel automatically bypass DND, or does the user have to explicitly allow the channel as an exception? Second, once a user has changed a channel's settings, my understanding is the app can no longer programmatically adjust that channel's importance or sound, which makes me question how to handle a channel I created with the wrong initial importance.

Assume Android 8.0 (API 26) through recent versions, with awareness that manufacturer skins may alter the channel UI.

1. Does channel importance alone determine DND behavior, or is a separate per-channel DND override required from the user?

2. Is deleting and recreating a channel with a new ID the only supported way to change defaults after user modification?

3. Is there a documented way to deep-link users directly to a specific channel's settings screen?