I'm not entirely sure, and I don't think the structure of the addresses themselves are at all different. I think what matters is how the BTC is sent. So on the Ledger, for example, it now prompts me if I'm using Legacy or Segwit. If I say Segwit, it shows me essentially an empty wallet (new addresses were created, as far as a I know). I want to use Segwit, I have to send my BTC to those new addresses (again, as far as a I know). After that, it will use the Segwit protocol for sending.