I have an old flatbed scanner that I occasionally use. I bought it in 2003 or 2004. For scanning I use an old 2010 Macbook Pro still running on MacOS X 10.6.8. The scanner software ist written for Power PC, and MacOS X is the last OS that can execute the software. The scanner still works perfectly fine. Some time ago I found out that there is third party software availiable that probably runs on recent macOS installations, but since I refuse to pay for it, I transfer the scanned documents with a thumb drive onto my M1 Macbook Pro. I tried to connect my recent Macbook Pro with my 2010 Macbook Pro via Bluetooth, but I couldn’t get them to transfer files between them, although they detect each other in the Bluetooth settings. I suspect that it is a compatibility issue, as there is a huge age gap between both operating systems (∼ 15 years)

Apples eco system does have pretty good safety features. As far as I have heard, Apple is indeed not up to sell user data outside their eco system. However, they collect data from their users and use it for their own purposes. It is always a good advice to go through each setting (of phone as well as laptop) and evaluate if it is needed for functionality (e.g. location services or access for the camera or contacts). Not only will this measurement reduce the amount of (usually) unneccessary data that is being transmitted otherwise, but it will also improve battery life as well.

Do you mean iCloud Mail? I assume it is as secure as all the other iCloud services themselves. Personally, I don’t use iCloud (except for the “Find my” feature). But you can set up any third party Email service with the Apple’s Mail app. I use Mailbox.org as email provider and have it set up with the Mail app on my iPhone. It works flawlessly. Third party email providers often come with additional costs (the lowest tier with Mailbox.org was 12 € each year when I switched from a freemail provider a couple of years ago). I don’t know if iCloud Mail is free of charge, other than additional storage space.