Can I use my apple account balance to pay using apple pay?

No, it is not possible.

Read again -> Related Article -> What you can buy with your Apple Gift Card or Apple Account balance

Apple Pay is the way to pay. It replaces your physical cards and cash with a method of payment that is private, easier and safer. Whether you pay in a store, on a website or in an app. This is the new payment.

it is actually the same as paying contactless with your bank card, only via the iPhone.

See -> Use Apple Pay for contactless payments on iPhone

Use Apple Pay for contactless payments on iPhone – Apple Support (UK)

Learn where to use Apple Pay

Learn where to use Apple Pay - Apple Support

What is apple bal?

If you mean Apple Cash, see -> Send money to someone in the Messages app.