replace video track and keep everything else
I ended up using this and it worked
ffmpeg -i &quot;original video file&quot; -i &quot;video file I want to insert&quot; -map_metadata 0 -map 0 -map -0:v:0 -map 1:v:0 output.mkv

this tells ffmpeg to remove the 1st video track from the 1st file and insert the 1st video track from the second file while retaining everything else as is.