User registration & login in Hyperledger fabric

I am working on a project where I need the functionality of user registration and user login. I need some suggestion. What would be the better way of achieving this task?

A.) Old school email & password OR
B.) By using public & private keys?

What I understand from option B is that we need to enroll a user from CA from Fabric-SDK. Once enrolment of user is done, we can generate a unique password-phrase like the same is happening in Meta-Mask. We can store that user info along with its username (the default username in fabric is user1, user2) with password-phrase.During user login, it will ask for user's private key or the unique password-phrase generated for its account. The certificates will be stored in hfc-keystore (the default dir used in Hyperledger fabric). Whenever a transaction is executed by that user say user akshay.sood, we will set the context of that user to fabric-client (Please correct if I am wrong in this case).

Here, My questions/queries are:

1.) What do you prefer (email/password or private/public keys and why?).
2.) If you prefer 2nd mechanism then how will you protect user keys and certificates stored in hfc-keystore dir. I mean it can be hacked or data can be stolen by hacker.
3.) How to recover user private/public key and certificate if it is deleted mistakenly from hfc-dir.
4.) Would you prefer using password-phrase? if no, what do you prefer?

Edits are welcome.
Please let me know if you have any suggestion/improvements

Your question is a choice of your preference, convenience & business needs. You can use either or both approaches in combination. Asking the user to keep or manage his private keys calls for a managed wallet. However, IMHO, if you are concerned about leakage or loss of private keys then you would need a Hardware Security Module that is specifically designed for this purpose.

P.S. Fabric & its examples store the keys in hfc folder for simplicity, although not recommended in real cases.