Also, the authorization preview on nsec should be even better. 
I see it working like this: 

1. on my website I have a "login with nsec" button 
2. opens use.nsec.app/auth or whatever
3. show all my nsec accounts, I pick one and callback my app. 

Straighforward, no libraries needed, no modals, no screen to maintain, no popups that require special browser permissions I'd rather discourage...