I dont agree with many things apple does at all, and I also think their password manager has flaws like revealing usernames without authentification.
It is pretty handy though, to have a file where the entries are stored unencrypted, and if the password manager detects an entry it prompts to decrypt exactly that field, maybe with a fingerprint.
KeepassDX needs to run in the background and be completely unlocked to even detect apps or password fields.
Kinda confused, you want a password manager that stores entries unencrypted but when you need them, the manager encrypts the entry and then prompts you for authetication to autofill the entry? That seems kinda dumb but if its just for convenience to not input your masterpassword everytime, keepassdx allows biometric unlocking. Think it'll take as much time as what you described without potentially exposing any unencrypted entry info
Edit: Before someone jumps at my throat, security wise using biometrics is also kinda a no no but I understand not everyone has the same threat model so go for it if you want
If I understand it correctly, the passwords are stored encrypted, but not the additional data, like website-URLs and app-names. This way the password manager only needs to temporarily decrypt a specific password when it's needed for auto-fill.
In regards to the passwords that's probably a bit safer than keeping all the data and the passwords unencrypted in memory. But the cost is that all the other data is stored unencrypted.