I switched from S22U to 14PM and don’t regret it at all. This is my first ever iPhone. My previous phones were all Galaxy phones starting from S7 edge. To answer your questions:

1. Bitwarden exists on the iOS App store. I did not notice much difference between iOS version and android’s version. You can use your existing email and master password to login and gain access to all your passwords that you synced on android. I’d say using bitwarden on apple keyboard is much easier than on samsung’s keyboard.
2. No YouTube vanced on iOS. You can download Adblock Pro and use YouTube ad free using Safari browser. I do the same. I’d suggest using Vinegar safari extension for YouTube.
3. All google apps are available for free on the App store. Not sure what apps you’re looking for. Apps that are useful to others may not be useful to you and wise versa.
4. You should create an Apple ID. I created it using my gmail ID. I continue to you my gmail ID for emails. Haven’t created an icloud ID and is not needed.
5. Airpods Pro 2 (better than Galaxy Buds Pro) and Apple Watch Series 8 or SE (much better than galaxy watch) in terms of of seem less connection and how fluid the UI is. Galaxy buds Pro will work on iPhone but you won’t be able to adjust the settings like you can on Samsung phones. I believe Galaxy buds plus and buds can be connected using the Galaxy wearable app on iOS. I’m not certain how Galaxy watch works when connected to an iPhone. Haven’t tried it.