How to merge videos side by side if one of them is cropped
Use

ffmpeg -i L.MOV -i R.MOV -filter_complex '[0:v]crop=in_w-28:in_h-28,scale=640:480,setsar=1,pad=iw*2:ih[int];[int][1:v]overlay=W/2:0[vid]' -map [vid] -c:v libx264 -crf 23 -preset veryfast LR.MOV


Since you want a zoomed-in effect, after cropping, you should rescale it back to 640x480. Your crop dimensions are disproportionate to the input dimensions so I have reset SAR to 1. You can skip this if you apply crop=in_w-28:in_h-21.



To apply the crop to the right video, use

ffmpeg -i L.MOV -i R.MOV -filter_complex '[1:v]crop=in_w-28:in_h-21,scale=640:480[int];[0:v]pad=iw*2:ih[left];[left][int]overlay=W/2:0[vid]' -map [vid] -c:v libx264 -crf 23 -preset veryfast LR.MOV