If you don't want to use Time Machine, you could use Carbonite ($5.00 a month cloud service backup) https://www.carbonite.com/en/cloud-backup/personal/buy/
There might be an app in the mac app store too
I'm not sure about Garageband, but theres always FL Studio Mobile (its $20 though and some instruments are extra)
https://itunes.apple.com/us/app/fl-studio-mobile-hd/id432850619?mt=8
Is Lightroom available in the app store, or is it only available through the adobe creative cloud subscription, also you may want to try gimp for Mac, it takes some getting used to but it is a powerful program.
Siri is available for the mac with macOS Sierra macOS - Apple
I guess Siri can perform basic tasks such as telling you how much space in free on your drive, or where that PDF you downloaded is. Probably get more features in subsequent releases
My Script Memo in the Appstore https://itunes.apple.com/us/app/myscript-memo/id446368116?mt=8
or MyScript Stylus https://itunes.apple.com/us/app/myscript-stylus-handwriting/id931394264?mt=8
Possibly contact Apple, or you could go to the site or setting (I'm not sure) and see if your still enrolled (even though you unenrolled) You could also look to see if the email has an option to unsubscribe to Apple's email service for beta releases
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Chrome is an excellent Browser however it uses a lot of resources (like Ram) but as a Christmas present this year supposedly Google is going to redesign it and it will use less resources.
Probably Safari, because it comes in with the OS. Chrome just updated their javascript engine to achieve faster performance but i'm unsure what that performance look like on respective Operating Systems