It is always safe to install custom ROMS for any device without bricking as your not violating the warranty issues. So it is always safe to install custom ROMS. Custom ROMS are always safe unless your are downloading it from a authentic source. All ROMS or custom ROMS in specific will be in .zip file.
Similarly one may ask, what is custom OS on Android?
“ROM” stands for “read-only memory.” A custom ROM replaces your device's Android operating system — normally stored in read-only memory — with a new version of the Android operating system. Custom ROMs are different from acquiring root access.
What does it mean to flash a custom ROM?
"Flashing a custom ROM" basically means to load a different version of the Android OS. This site actually explains it very well. A custom ROM is the full Android OS customized by the ROM builder usually to make it faster, provide better battery-life or add new features.
What is root and custom rom?
Rooting, in a nutshell, is the process that provides users with full administrator control and access to an Android smartphone or tablet. In rooting culture, we'd call that "flashing a custom ROM." The process of rooting an Android phone varies for each device, but seems to have been streamlined over time.