You have full control of where you place the subtitles with the ass format aegisub uses by default(but others support too), you can even put both at the bottom, one left and one right, change the color, stuff like that: https://fileformats.fandom.com/wiki/SubStation_Alpha#Data_types
Burning subs into a video is more complicated(Only way I know is using avisynth which is pretty complicated but other easier software likely also have that function) and if it's just for comparison sake, much easier to use a .ass subtitle.
Edit: To give you an idea, this was done with subtitle edit by setting 2 styles(after converting the vtt to ass), one for top left and the other for top right with a 1000 pixel margin on the opposite side so they don't overlap. You set one style to your currently open sub for all lines, then you append your second subtitle(there's a thing for that in tools, don't sync anything, leave as-is) and you set the second style for all lines of that second subtitle(shift + end will select the lines from the currently selected one to the end, shift + home does the opposite) and it's that easy.

Burning subs into a video is more complicated(Only way I know is using avisynth which is pretty complicated but other easier software likely also have that function) and if it's just for comparison sake, much easier to use a .ass subtitle.
Edit: To give you an idea, this was done with subtitle edit by setting 2 styles(after converting the vtt to ass), one for top left and the other for top right with a 1000 pixel margin on the opposite side so they don't overlap. You set one style to your currently open sub for all lines, then you append your second subtitle(there's a thing for that in tools, don't sync anything, leave as-is) and you set the second style for all lines of that second subtitle(shift + end will select the lines from the currently selected one to the end, shift + home does the opposite) and it's that easy.

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