If I want to get an OAuth token to follow/sub with an account. What scope should I use?
user_follows_edit scope you can use the Follow Channel endpoint https://dev.twitch.tv/docs/v5/reference/users#follow-channel to follow a channel.
It’s not possible at all for 3rd parties to cause a user to subscribe to another channel. Subscribing to a channel has to be done by the user themselves through Twitch.