They have some things in common (OSTree, Flatpak) but have different ancestors (Fedora/RedHat vs. Debian/Ubuntu). Additionally, EOS has a customized User Interface based on GNOME and is generally more tailored to provide a usable out-of-box Experience for novice users. It also includes a great set of applications for educational purposes.
Can’t anser the Nvidia question as i don’t have any device with a NVidia GPU
ZRAM is activated per default on EOS
Can’t answer the SNAP question, as i’m not associated with Endless and don’t know their internal plans.
Most applications included per default in EOS are GNOME based, also the ones built by Endless
From other threads in the forum it seems that the proprietary NVIDIA driver included with EOS supports hybrid graphics. Just try EOS, you will be satisfied. I used many different Linux distributions over the last two decades (Ubuntu, Debian, openSUSE, Fedora, …) and settled with EOS about 18 months ago. Never regretted it a single second.