I don't know about iOS but if you use an Android you can try Bitwarden. It detects credential fields and when you tap in them a little popup appers that offers Bitwarden to auto-fill these fields. When you then tap on that it opens Bitwarden and it offers all fitting entries from your vault. Select the one you want to use and then it fills the fields.
Maybe that's what you're looking for? I really love that feature.

On Android, I'd recommend looking into Keepass2Android. I don't necessarily guarantee that it'll solve your issues, but it has lots of options and is fully compatible. At the very least, it always offer autofill for me, even when locked and there's various methods of Quick-Unlock.

As for your general problem of having all entries unlocked, that's just a necessary trait of local password managers. I don't really see it as a problem though, since I don't really see a situation where an attacker would only have access to my unlocked passwords, but not also my master password, rendering selective unlocking of entries pointless anyway.

I'd also consider getting a hardware key (YubiKey) and use that in combination with a short password for your password. Both KeePassXC and Keepass2Android support them. More secure and much more comfortable than your current solution.

On android, Make sure KeePassDX as the default auto fill service and also give display pop up windows while running in the background permission from system settings to the app. If that doesn't solve your problem, simply use KeePassDX magikeyboard feature.