safest is situation dependent and depends on how you think about security with regard to your nostr private key. for me, running the device at home works well. it's not going to be as secure as using amber at the moment. i'm using it daily with jumble.social on mobile and desktop and think it's very good. we're exploring a couple of options for encrypting the keys. it could be a hardware upgrade if we use the tropic square SE, or an alternative would be a software update that does something similar to how the Jade secures keys with a blind oracle. I highly doubt we'll do this though tbh.