This is a good topic and indeed, I think we covered it at our General meeting in April of last year (not a bad idea to do it again soon!). Our Special Interest Group meetings cover backups at least once a year as well.
For what it's worth, here are my general thoughts on backup strategies:
For most Mac users, the combination of Time Machine (local, full backup) and iCloud syncing (either just the core synced apps or optional music and photos syncing for a modest price) should do the job nicely for a price ranging from free to extremely modest. I've always advocated for additionally creating a bootable backup of your present system using a tool like Carbon Copy Cloner or SuperDuper (these clones, which should be stored on another external drive -- not the one you have your Time Machine backup on) can be useful for recovering quickly from a drive crash.
Online (cloud) backup using services like Backblaze or iDrive are also good options for Mac users that go beyond what Apple offers by backing up the entire contents of your drive (and updating the backup) to a secure server so the data is safe even if your local backups are destroyed/inaccessible. Some Mac users have much more advanced needs (like needing to keep more than one Mac in total sync), and the best option I know of for "advanced/complex" backup strategies is ChronoSync from Econ Technologies in Florida. Full disclosure, I worked for the company back in its earliest days -- but this does not influence my opinion of the program's modern abilities.
For iOS devices, there are a number of options but the best by far is iCloud, as it is so deeply integrated. There are some free options for things like documents and photos/videos, but remember -- they're free because you are giving the host company total access to your stuff and a permanent license to use them anyway they wish. For me that's way too high a trade-off, considering how cheap secure options are, but you may feel differently.
As mentioned, you can also backup your iOS devices directly onto the Mac if you like, but of course these take up a lot of space on the Mac and get included in the backups of the Mac you make, which makes them take longer.