How to join these three FFmpeg instances into one command
ffmpeg -y -i inputStream \
 -row-mt 1 -s 1280x720 -b:v 1024k -minrate 512k -maxrate 1485k  
 -tile-columns 2 -g 240 -threads 8 -quality good -crf 32 -c:v libvpx-vp9 -c:a libvorbis hd \
 -row-mt 1 -s 640x480 -b:v 750k -minrate 375k -maxrate 1088k \
 -tile-columns 1 -g 240 -threads 4 -quality good -crf 33 -c:v libvpx-vp9 -c:a libvorbis fsd \
 -row-mt 1 -s 640x480 -b:v 512k -minrate 256k -maxrate 742k \
 -tile-columns 1 -g 240 -threads 4 -quality good -crf 34 -c:v libvpx-vp9 -c:a libvorbis sd


After specifying your input(s), all audio/video/subtitle options are designated for the next output, so you may write different options for different outputs.

From FFmpeg documentation, Chapter 2 Description:


  Do not mix input and output files – first specify all input files, then all output files. Also do not mix options which belong to different files. All options apply ONLY to the next input or output file and are reset between files.