Accounts 
Frontier provides two different strategies for handling H160 addresses.
H256 -> H160 mapping 
The first strategy consists of a truncated hash scheme, where the first 160 LE bytes of a H256 address are used to form the H160 address.
AccountId32 is the Account type used for frame_system::pallet::Config::AccountId.
The Runtime's Signature type is configured as sp_runtime::MultiSignature, which means signatures can be:
Sr25519Ed25519ECDSA
Native H160 via AccountId20 
The second strategy consists of using fp-account so that AccountId20 is the Account type used for frame_system::pallet::Config::AccountId.
The Runtime's Signature type is configured as EthereumSigner, which means only ECDSA signatures are supported.