Hi Chat
I am new to Linux but from what I understand with the changes to the packages management systems and the inclusion of snaps and flat packs what will be the main disparities between the Linux flavours? Sorry if this is a stupid question.
I am no Linux developer, but from what I understood, snaps goal is mostly to target applications, the same way as Android or iOS applications do.
The reason behind this is because on classic linux distributions, package versions are frozen after release (except for security updates). That means that for example you will never get the latest version of your favorite software, to avoid breaking libraries versions that might also be used by your OS.
Snaps provide dependencies directly in the package, so you can use a different version of a library that is already installed on your system and thus have the latest versions of your favorite softwares.
So to summary, deb packages will still be used for the core os, but snaps will be used for applications.
It’s Flatpak that target mostly application (and that is destined to be used in conjonction with a way of handling the “host” part), Snap on the contrary can package more than just the apps 
There is an all-snap version of Ubuntu for instance (Ubuntu Core). If I’m not wrong, it might even be possible to package flatpak as a snap.
Well, there will be distributions that’ll prefer other way of distributing apps, and apps aren’t even the main attraction of many distributions (they are important, of course, but not what people think about when they think about these distro). And even with the existence of cross-distro store, some distro will certainly have their own flatpak/snap store for some case.
How the base will be updated, different shells (many distributions now use their own shell), atomic read-only base (like ostree) or traditionnal base… And maybe many other things that I’m not thinking about. A distribution is way more than a collection of applications. If the burden of application is taken a bit away, it might free some maintainer/packager to work on other things if they want too.
The biggest difference will be that there will be two good ways to target many distributions at once (Flatpak and Snap) for apps developpers.