In general, if you're sure that the file comes from a trusted source and has a valid digital signature, it should be safe to execute.
after the installation is finished. Once the drivers are installed, the installer file itself is no longer needed and can be safely removed to save space. Device Manager to see if your Realtek drivers are currently up to date? what is rtk-nic-driver-installer.sfx.exe
rtk-nic-driver-installer.sfx.exe a self-extracting executable file used to install drivers for Realtek Network Interface Controllers (NIC) What Is rtk-nic-driver-installer