There is - usually - only post-update problems if you have customized your system heavily.
Just like Arch - custom packages are unsupported - and Manjaro is as stable as Arch - suffice you know what you are doing.
Enlighten yourself on best practise for updates
A few basic rules - if you want to avoid breakages
- Do not stray from upstream
- Do not exagerate custom packages
- Do not employ all likes of custom themes