In a case if I will one day consider using another distro alongside Fedora utilizing the same /home (like Nobara ones it becomes mature), should I create root/home/swap as separate partitions now? Or will I be able to connect to Fedora’s “floating-size” /home if it will all be on a single partition?
GNOME’s installer seems to have a pretty complicated manual partitioning process (I tried doing it on, I think, KDE or Cinnamon a long time ago—it had a simple and intuitive silder to allocate free space, while GNOME provides a confusing menu). Can I use some easy-to-learn program to allocate partitions after installing and using Fedora for some time?
Fedora by default uses btrfs for the root and home partitions (subvolumes)
As I understand it nobara does not use btrfs, so using the same home partitions probably would not be possible. Both use zram for swap so that is probably not an issue. The root partition would obviously also be different. Moving between distros would be best done by doing a backup of the users data on the outgoing OS and restoring that data on the new OS
Additionally, I understand that nobara uses systemd-boot so grub interface and config would also disappear, as well as not using /boot for the kernel files. Those are moved into the esp partition.
You can mount the btrfs home sub-volume from another linux with btrfs support (there could be issues with older distros), but there can be clashes with configuration data in hidden subdirectories like ~/local, ~/.config, as well as app-specific directories. Before btrfs and pods I have shared data across linux distros by using /home/distro/user directories and then putting directories to be shared like Documents, Pictures, etc., (say on /home/shared/), with symbolic links in the /home/distro/user directories). These days I rarely need to install a different distro as I can use pods for the use cases that once needed access to a 2nd distro.