It used to be that different versions, namely kmod and tmod, were required for certain exclusive encoding features such as "aq-mode 3". However, all relevant features have been included in the upstream x264 builds since August 2018.
However, this is not entirely true. For example, fade-compensation and film grain optimization are not included in mainline x264.
This section mentions:
However, this is not entirely true. For example, fade-compensation and film grain optimization are not included in mainline x264.