Wallet validation methods (centralized, SPV, etc.) - please clarify for Ledger and in general
The answer is simple: Ledger is not a wallet, it's a device to improve the security of a wallet. Everything depends on what wallet you use it with.

It's a hardware signing device. They're often called "hardware wallets", but that is a misleading name. It does not manage your money, or send or receive transactions. It's simply a secure, offline, device to hold your private keys, and sign transactions provided to it.

As such, it's really just a way to improve the security of an actual wallet, which it is used in conjunction with.
Ledger has their own, but several more common software wallets (e.g. Electrum, Green, Bitcoin Core through the HWI toolset, ...) can use Ledgers as a signing device. The security and privacy tradeoffs you get depend on the software you use it with.