As a general rule you should enable
remi-modular (but all three of these should already be enabled). These repos together contain the packages and module streams you expected to install from remi.
These repos break down as follows:
remi-safe contains packages which are required by other packages in the main repos remi and remi-modular, but are not included with the Linux distribution you are using. It is called "safe" because it does not replace any packages shipped by the distro.
remi and remi-modular contain the packages you are interested in. These may replace and override packages and module streams included by your distribution. Module streams are included in the remi-modular repo, and other packages are in the remi repo.
The remi-test and remi-modular-test contain updates which are being tested before general release in the remi and remi-modular repos. You generally won't enable these, but if you are having a problem with a package, you might get early access to an update through these repos.
The debuginfo repos contain debuginfo RPMs which are used when debugging a program or through automatic bug reporting. You also won't enable these repos; ABRT will automatically install packages from them if needed for bug reporting, and you would manually install them (e.g. to run the debugger yourself) with
dnf debuginfo-install <package>.