Antwort auf: Wechsel von Ledger zu Trezor

1. yes you can import your existing seed
2. yes ledger will still have access to your wallet if you leave the seed within it

If you switch to Trezor because you are concerned that ledger (the company) might have your seed already or might extract it in the future: set your Trezor up as new wallet with a fresh seed and transfer your assets to the new wallets.

To quote the butcher from Diablo _ahh, fresh seed!_