Native segwit addresses are not encoded using base58, but using a different encoding system called bech32. The details can be found in BIP 173. For the segwit v1+ addresses that will be used for Taproot, see the amended bech32m encoding in BIP 350.
In short, the addresses consist of:
A human readable part, which is bc for Bitcoin mainnet segwit addresses.
P2WPKH and bech32 are not quite synonymous.
Native segwit describes a type of output schema in which the scriptPubKey (the "locking script") is composed of a witness version and a witness program. P2WPKH is a native segwit v0 output type.
Bech32 refers to an encoding scheme and an address format to represent a recipient's scriptPubKey in out-of-...