Ideally, any service like that should be used with a signing app like Amber. Which coinos doesnt support, I dont believe. Putting your nsec anywhere is incredibly dangerous. Although Im guilty of doing it a bit. Yakihone sounds like a whole nostr client so Im not sure what their setup is like, havent really heard of them. Yea, it can definitely be frustrating and unintuitive. Better tools can be built though, but Im sure itll be a slow process