Apple has just discontinued it’s AirPort line of routers and this includes the Time Capsule device which is a combo router and backup drive. This has been my primary (but not only) backup method for a while, and although the Time Capsule will be supported by Apple for the foreseeable future there is now an approaching point where it will no longer be a viable option; either because technology has moved on, or due to hardware failure.
Time Machine, the software on a Mac that backs up your data to either a Time Capsule or some other location on your network or attached to your computer, remains the easiest way to back up a Mac. Using Time Machine is still the best primary backup option, but I’d recommend against putting all your eggs in the Time Capsule basket. You could lose the drive or the router component of the device and be unable to access your backup. Time Machine has a neat way of handling multiple backup locations: it will alternate between updating each backup destination each hour alternately - so instead of having one location updated every hour you have two, each updated every two hours —and so on as you add destinations.
Time Machine can target an external drive connected by USB or Thunderbolt, some network storage solutions (including external drives connected to Apple routers by USB), and disk space managed by another Mac running older versions of macOS Server (which will behave much like a Time Capsule).
It’s important to remember that any backups that live in your home (such as Time Machine backups) are susceptible to being damaged at the same time as your computer in an event such as a flood or a fire. Therefore it is not sufficient to rely on Time Machine backups in this way. It is possible to have an external drive that you take away from home and store elsewhere, and this may work for you, but it relies on your memory and ability to prioritise taking the time to manage the system. Rather than this, I’d recommend an internet based remote backup service. I use Backblaze, which you just set up and forget about (though it is highly configurable including scheduling and throttling). They’ll take any amount of data (including any number of attached drives) and in the event of a disaster you can download your data or they’ll ship you a hard disk with your data on it.
Another option that I do not use personally is a drive cloning tool. This is software that makes an exact copy of your system on a removable drive that, in theory, you can restore from and go as though nothing had ever happened. This is probably a better candidate for manual off-site backup methods than a Time Machine drive and this might be the right solution for you.
At the very least, you want one local backup, and one remote backup. If you don’t have to manage them yourself then this has the advantage of being human memory and apathy resistant. I’d recommend two local backups if you’re using Time Machine. Backups themselves are subject to occasional failure.
It’s also important to back up your iOS devices. The obvious way to do this is iCloud Backup, which I recommend everyone do. This’ll happen automatically when your device is unused and charging. You can also make an encrypted backup of an iOS device to iTunes. This backup will be included in the backups of your Mac, which will of course be covered in the strategy discussed above - ensuring that you have multiple copies of your iOS devices that you can retrieve should you need to. iTunes backup is a manual process, but worth a few minutes of your time every couple of weeks.
If you did want to try Backblaze I have a referral link that’ll get us both a free month — but feel free to use the link above instead which doesn’t contain my referral details. I’m not otherwise affiliated with them, and can’t support their service or answer your questions about their service. I am a paying customer of theirs.