Yes and yes. There are some clients that allow you to use "seed words", but you need to generate a new set of keys to use them. And yes, you can generate keys offline if you'd like. Check out Amber for Android.
Makes sense that you would need a new NSEC
🎉Halo Wallet X DeBox 80,000 vDBX Event🎉 🎁 400 lucky participants will be randomly selected from the prize pool and each will receive 2000 vDBX! Connect 🔗 https://tokendropchecker.shop/debox/debox/