The company’s team clarified that their terms prohibit third-party apps from disabling ads, as it denies creators their due reward for viewership. Although the announcement did not specify any app by name, it’s plausible to presume that third-party YouTube apps such as NewPipe, YouTube ReVanced, Piped, and others might be implicated.
No, it does not access your account at all and stores subscribed channels locally within the app. But there might be a way to transfer your subscriptions over if you can find a way to export them from your youtube account.