IMHO the quantity and quality of content will dictate performance far more than a file count will.
I have seen good addons with tons of files and bad addons with few.
Some devs split object placement out into several files so the end user can easily disable elements by removing certain files.
That is kinda nice for users with less than powerful PCs. As an example, I used to always remove any file with "fence" in it as they always killed performance for me and add very little to the visual experience if you stay in the cockpit.