What is clear is that ethereum is not on the list because ethereum fee is sick and why is there no stellar on the list? in my opinion, because your project concerns online payment using stellar it seems more suitable because besides being a low cost blockchain, the goal is also a financial problem or maybe Polkadot is similar to ethereum but costs the transaction is very cheap, the drawback is that maybe this still new blockchain, so there are still very few tokens made with polkadot.