Just in passing, there is considerable difference between "sync files" approach to backing up your data (no matter how many duplicate copies you make for presumed reliability concerns) and true "backup" (which would provide "daily recovery" capability of anything you've had on your system on any day over some past period of time, rather than just keeping a "current copy").
In other words, while I too run Macrium Reflect for once-weekly "system image" backups to a 2TB external USB 3.0 drive (retaining 6 generations) on one system and twice-weekly "system image" backups on my HTPC system (to potentially protect myself against losing too much copy-protected recorded TV subject to DRM encrypting issues where the WMC encryption key is date-sensitive), I use NovaBACKUP as my true "data" backup mechanism. Again, the 2TB external USB 3.0 drive is the target for the backups.
The NovaBACKUP scheme involves running a FULL backup (i.e. of EVERYTHING on all of my internal hard drives except for the \Windows folder on C) on the 1st of every month. Then on every subsequent day of the month I run a "daily INCREMENTAL" backup, which backs up only those folder/files which have been created or changed since the previous backup (either FULL or INCREMENTAL), i.e. in the past 24 hours. As long as a file exists when the nightly INCREMENTAL backup is run, it will get onto that backup dataset and therefore be available for possible recovery at any time in the future should it be necessary or desired.
I retain 4 complete "month-based sets" (i.e. monthly FULL on the 1st plus daily INCREMENTAL for every other day), so I have the ability to recover ANY folder/file which existed ON ANY DAY (at least when that day's FULL or INCREMENTAL backup got run) in the past 4 months. This satisfies my paranoia that I might want to recover some file I previously had deleted or replaced (so that it is no longer on my system or available in the form I truly now need), where the more current version may be defective or invalid (or even missing!) and I need to get a prior version to satisfy this particular situation's needs.
In other words, the ability to selectively recover ANY date's version of a folder/file going back any length of time into the past (4 months in my case, with daily recovery capability for ANY day in that 4 month period) can ONLY be provided if (a) you're using suitable backup software that provides this date-sensitive recovery capability for each folder/file that has been backed up on ANY dataset (i.e. FULL or INCREMENTAL) covering the entire period represented by how many "month-based sets" are available, and (b) you actually have retained as many "month-based sets" as you need to guarantee recoverability to meet your personal or professional (or paranoid) needs.
So Macrium Reflect provides my Windows system backup (i.e. everything on C, including \Windows). And NovaBACKUP provides my "data" backup. I do not use "sync" as a backup method, although I certainly do keep my two desktops and laptop "in sync"... but using Beyond Compare.
NOTE: Macrium Reflect also provides this "data backup" capability in addition to its "system image" backup capability. But I much prefer the GUI and additional features of NovaBACKUP, which is why I don't use Macrium Reflect for "data" backups. That's actually the same reasoning (in reverse) that I use Macrium Reflect for "system image" backups, even though NovaBACKUP also has a similar "system image" capability, much preferring how Macrium Reflect works for this task.