Give me advice on creating a loyalty program in the bank

Hey. I am a programmer and I have a task to create a loyalty program in a bank on blockchain technology.
Users of the bank will receive tokens as a cashback and spend them on clothing, food and so on.

I think to create the loyalty tokens on the platform Ethereum or Waves.

The cost of the Ethereum transactions is too high ($ 0.7 - 1.5), but it has smart contracts.
Waves are less popular, there are no smart contracts, but transactions are cheaper ($ 0.015).

Please tell me about other platforms that you know.
Do I need smart contracts in this area?
Does it make sense to store tokens in the open ledger, maybe I should use the permissioned blockchain?
Are there any successful projects in the market that implement loyalty programs using blockchain?