Second, you are listing tools like cmake and meson. Note that these are NOT build systems but they are META BUILD SYSTEMS. Meta build systems are tools that don't really build your project themselves... instead they rely on tools like Make, Ninja and Beast to build it for you. You must have seen that Cmake emits a Makefile (or Ninja file depending upon your choice). So comparison in speed to meson will not be appropriate. (Let us just call them high level build tools)
About your third query... Well Beast is easy enough to compile. If you don't want to compile it, you can directly download the system binaries at https://github.com/GauravDawra/Beast/releases/tag/v1.1.0
I'm currently using Make to compile Beast because I originally compiled it using Make. It will soon move on to CMake. Please note that it is totally OK to use flex and bison. You don't even need them since I have already provided the cpp/h files generated by them on github!