FlatPak and snaps are not only solving the universal packing problem, but in addition: providing necessary libraries which are not present on the main system; an be installed on multiple architectures (x86, arm, etc); sandboxed.
My problem with matrix is that you need email address to use it. Compared to the irc, where you could just use whatever name and ask questions straight away. Most distros I used came with an irc client preinstalled and preconfigured to connect to the support channel when launched. In my opinion that is more beginner friendly.
Replace the HDD with SSD. It will run faster. You can configure any DE to look similar to windows, maybe Gnome to the lesser extend. One think to keep in mind when choosing the distro, you have to support it. Good luck.
A bit of history. The first universal packaging format was snap by Canonical and used to be called Click apps and it was made for the Ubuntu mobile OS and later to the Ubuntu desktop. Red Hat in response to that created the FlatPak format. The AppImages are community effort.
Have a look at Super Productivity it is a todo list app with projects, time tracking, break time reminder. It is completely offline, no registration required.