Is stripe and PayPal the only way for clients to make payment?

Yes, Stripe has an Apple Pay integration as well.

Please note, If a client pays with Apple Pay through the app, Apple will take a 30% commission. But if clients pay with Apple Pay through a browser, no commission will be taken.

When adding a client, you can choose that the client doesn't need to pay through Kahunas. So, it will be up to you how to receive the client's payment.