think as you want a blockchain that has fees on transfers, there are many blockchains and you should read all docs and codes to find which parts of that codes are related to manipulating balances so it is extremely hard, but Polkadot architecture allows you and pointed to where you can do that. FRAME is the power of Polkadot. there are some good information about design architecture here https://docs.substrate.io/v3/runtime/frame/