Good on you to finally get into it, I switched to something systematic only very recently myself (previously it was "copy important stuff to an external HDD whenever I think of it").
The one thing that I learned (luckily the easy-ish way) is: test your backup. Yes, it's annoying, but since you rarely (ideally never!) will need to restore the backup it's incredibly easy to think that everything in your system is working and it either never having worked properly or it somehow started failing at some point.
A backup solution that has never been tested via a full restore of at least something has to be assumed to be broken.
Which reminds me: I have to set up the cron job to periodically test a percentage of all backed up data.
I decided to use Kopia, btw, but can't really say if that's well-suited for your goals.