SeedSigner is not a wallet and does not store your keys; you input your seed words to sign a transaction (the device can help you make a QR code to speed that up). You have to use it with a wallet; it works great with Sparrow wallet.

As for importing or migrating to another cold wallet, you only need the seed words, and you should note the fingerprint and derivation path.

nostr:npub1rxysxnjkhrmqd3ey73dp9n5y5yvyzcs64acc9g0k2epcpwwyya4spvhnp8 has tons of tutorial videos on YouTube.