Can users subscribe to a channel? Are channel subscriptions payable?

Yes, they can subscribe to all channels that they like and you can set subscription for them to pay and enjoy

Note: The subscribe option will only be visible for channels that have set the subscription price.

Where can users find the channels they are subscribed to?

Users can find the list of channels they are subscribed to under their profile name and then click on Subscriptions.

Are channel subscriptions only free or is there an option to create paid subscriptions for channels?

Channel subscriptions can also be offered for free or paid subscription. Users can follow channels to find the contents like.