iOS/iPadOS Syncs Unrequested Data to iCloud

I sync only a very limited subset of my data to iCloud. Every time (or at least almost every time) that I:

1. Update the OS, or
2. Sign out then back into iCloud

my devices turn on additional data to be synced to iCloud without any notification that these changes have been made. This seems to happen/have happened on multiple versions of iOS/iPadOS dating back years and on devices as disparate as an iPhone 5S, iPad Mini 2, iPad Air 3, iPhone SE 2, etc.

The most "popular" categories of data turned on without notice are Game Center (I think this one auto-enables 100% of the time, and I have never installed or played a game on any of my iDevices), Photos, Home, Siri (I don't use Siri, ever), and iCloud Drive (although it seems like it's been a while since this one got auto-enabled).

This behavior is annoying and it causes problems because, theoretically, data get moved around/changed when synced to iCloud (e.g., photo resolutions may be degraded on the device when the full-resolution photos are stored on iCloud). It then takes me time to figure out how to undo the settings without accidentally losing data.

I usually catch these, but it takes only a moment of unintended synchronization to cause issues.

Recently, I found that Photos were (secretly) being synced, so I turned off iCloud syncing for Photos. I selected saving data to the device (at least it's a better notice than the old "You will lose data" message that Apple used to display). Today, I received a friendly email from Apple stating that I needed to download my full-resolution photos and videos within the 30 day grace period or they would be gone forever. Nice, but never should have come to this. The instructions say:

To download your photos and videos to an iPhone, iPad or iPod touch with iOS 8 or later: 

1. Connect to a power source and Wi-Fi. 

2. Go to settings, tap on your account, tap iCloud, and then select Photos. 

3. Tap Download and Keep Originals.

Hmmmmm...can't do what the experts at Apple say, because the instructions don't match my screen. Perhaps if I turned iCloud photo syncing back on, I would see the correct user interface, but, of course, the instructions don't say that, and I don't want to turn syncing back on unless absolutely necessary.

Soooooo...at this point, I'm ****** off because this keeps happening, I'm ****** off because the scare email from Apple contains instructions that can't be executed as written, and I'm confused as to how to make this insane unrequested-auto-iCloud-enabling mess stop.

I could use help with two things:

1. How am I actually supposed to interpret Apple's instructions to download my full-resolution photos and videos?
2. How to I stop the OS from secretly and repeatedly auto-enabling iCloud backup for categories of data that I have not selected for backup?

Thanks!

Gordie