There are two flavors of RMF called MTW and RSW. MTW supports 16-bit integer and 32/64-bit floating point data in a single channel and aimed to store DEM data. RSW is a general purpose raster. It supports single channel colormapped or three channel RGB images. Only 8-bit data can be stored in RSW. Simple georeferencing can be provided for both image types.
NUM_THREADS=number_of_threads/ALL_CPUS: (From GDAL 2.4) Enable multi-threaded compression by specifying the number of worker threads. Default is compression in the main thread.