Different OpenGL drivers - Nvidia, Mesa, Intel - which one to choose?

Usually it's enough to use:

LD_LIBRARY_PATH=/path/to/libgl # Ubuntu (/usr/lib/libGL.so)

There's also LIBGL_DRIVERS_PATH. And if all doesn't work, you can still use LD_PRELOAD to load another libgl first.

But there is no guarantee, which libGL is used by which App to compile- and/or run-time.???