I don’t think this is specifically related to cut scenes however i also started out with a single scene and ultimately had to split out into scenes because of the 4gb build limit in unity. There is also initial application load time to consider. I think unity 2020 removes this limit. See this thread for more details:
Bug: 4GB limit to Textures in standalone build #:~:text=Unity%20Technologies&text=This%20is%20a%20limit%20of,limit%20of%20which%20is%204GB.