If you can spend 20$ to get a sale, if adsets spent 20 with zero sales, I would kill it then. Killing on adset level works better for me If it works for the last 3 days and the average ROAS falls below BE ROAS, I would kill it. If I kill the adset today, I can reactivate the same adset tomorrow to see if it gets back to good performance.
With ATC if you know you should get ATC within first $10 of spend, and you don’t get it, I would kill it.
Typically adsets either perform from start or don’t perform so that’s how I would do it.