1) A VoidSigner is a simple Signer which cannot sign.
It is useful as a read-only signer, when an API requires a Signer as a parameter, but it is known only read-only operations will be carried.

address = "0x8ba1f109551bD432803012645Ac136ddd64DBA72"
signer = new ethers.VoidSigner(address, provider)


2) Wallet
The Wallet class inherits Signer and can sign transactions and messages using a private key as a standard Externally Owned Account (EOA).

3) JsonRpcSigner
A JsonRpcSigner is a simple Signer which is backed by a connected JsonRpcProvider

jsonRpcProvider.getSigner( [ addressOrIndex ] ) ⇒ JsonRpcSignersource
Returns a JsonRpcSigner which is managed by this Ethereum node, at addressOrIndex. If no addressOrIndex is provided, the first account (account #0) is used.



The wallet knows its own private key. The JSON RPC signer sends a request to the provider, which responds with a signed request. The JSON RPC signer does not see the key itself.
So a wallet is capable of signing transactions directly, whereas an RPC signer can only request that the provider sign transactions.