Unless you want to go as far as installing a custom ROM, which may not even possible because the phone is so new, the best thing to do is don’t sign into a Google account. Sideload the Aurora Store, an F-Droid frontend like Droid-ify, and Obtanium.
The first one lets you sign in anonymously to a random proxy account to download Google play apps without needing to sign into a personal Google account. You can also sign in if you really need to for things like apps you’ve paid for and it still fuzzes some of the analytics Google collects on you, but eliminates a lot of the benefit.
The 2nd one is going to be your primary place to find open source apps or open source versions of apps that have both a Google play and an F-Droid version. For example, the media streaming app Jellyfin has both, but only the Google Play version has the ability to Cast to Chromecast devices because it requires proprietary Google code.
The last one, Obtanium, lets you download apps directly from Github/lab/codeburg/etc repositories from developers that host their apks there directly instead of relying on the stores. This bypasses some security checks that stores like F-Droid use, so it’s a little more on you to trust apps this way, but you usually get updates faster. For example, I have things like Thunder (a Lemmy client) and IronFox Browser installed through Obtanium.
To answer some of your specific questions, a lot of the pre-installed apps aren’t going to let you remove them entirely. You can disable and remove their saved data though, which is still good to do so they at least don’t suck battery. And if you ever need the app, you can re-enable it. Actually removing them requires plugging your phone into your computer and using command line android tools to remove them manually.
You should easily be able to set up mail forwarding from a Gmail account to Proton or elsewhere, but know that this eliminates some benefit, as it means that Google is still getting a copy of the email before it gets forwarded to Proton and that means they can read and obtain whatever information they want from it if they ever felt the need.
Was wondering this too. If they’re officially associated with the Tamriel Rebuilt mod, which is a huge and long developed project, that’s a really bad look.