My experience is that an upgrade or backup and restore rarely works well when going across major version changes. You will get weird inexplicable changes because some function that an addon uses has had a version bump and the variables that once worked have changed.
Its really best to do a fresh install. However once you have successfully carried out an install and setup on one box - its generally successful to do a backup and then use that to setup the other boxes because they are all running the same versions.
I did that at first, and it was sort of functional - but my skin was just all messed up with missing functionality. Its more likely to work if you stick to vanilla estuary.
To be truly frank Matrix brings nothing useful to the table over Leia. Its mainly all about the Python shift. I run Leia on my main Livingroom system and I run Matrix on my N2 bedroom system. I only run Matrix as a favour to the team for testing purposes - and I have lost a few bits of very useful functionality in the process.
This is not to dis Matrix which runs really well on the N2, but I am not going to ecourage anyone to make the jump without them having a good reason to do so.
I think it depends from addons you use. Some of them can stop working (due to Python version bump) and you will be forced to update or reinstall them.
In my case, upgrade from Leia to Matrix went just fine. Tvheadend and simple iptv clients addons - no problem (but need to update them). But Netflix has stopped working, need to install new version from Matrix repo.
Rare cases: update can prevent Kodi from run, especially with some incompatible skin applied before update.