Turning on the same auto-repost and the same Slack notification on every post is not automation.
Each connected channel now has its own settings page with an Automation defaults section. Set what should happen by default for that channel: auto-comment, auto-like or react, auto-repost, and whether to notify Slack or Discord.
New posts on that channel start with those settings already applied. You can still change them on any individual post, which stays the exception rather than the routine.
The same page holds that channel's posting schedule, timezone, and link tracking, so everything specific to one account is in one place.