Hi there, the thread is already quite full so not want to spam
Really cool that you made the switch! How do you get your apps? All from Google Play? Because otherwise this isnt very clear.
The password manager on iOS is different from KeepassDX, I dont know about Bitwarden. Have you tried disabling battery optimization for Bitwarden?
On iOS the system stores what logins you want unencrypted, or at least quickly accessible. Only the passwords need to be decrypted or unlocked on demand. This is a waaay better approach than traditional password managers, if you trust the device, metadata is unencrypted, and you want to use autofill.
I personally use the vanadium and Mull password managers, which work well. I use KeepassDX with Syncthing-Fork, to have my passwords everywhere. But I also use the synced Firefox password manager. Poorly firefox on Android is not very secure but has support for great addons like UBlock-Origin, which I recently got setup to use for javascript blocking as well.
The app ecosystem is way more chaotic, as they are all FOSS. For calendar I like Fossify Calendar. The proton ecosystem may be easy to use with sync and all, and look nice.
If you flee the grip of big brother, you will need multiple solutions likely.
For filesharing, use LocalSend. It is not as easy, but you can use it over wifi and hotspot, it works better than Bluetooth.
Mail, well you should get a different mail provider. Privacyguides.org has a big list.
Thunderbird Android is a nice and easy to use App.
For navigation, you can use Google Maps as webapp from Vanadium. Dont know about apple maps, but that should be good.
You can also always install apps. If you want to isolate them, use the private space. If you want to have another isolated location, install shelter and setup the work profile.
For navigation I use OSMAnd~ which you can get paid from the PlayStore or for free from F-Droid. It is a very powerful but sometimes buggy and pretty complex app.
OrganicMaps is easier to use and very smooth