This depends not only on the computer but on what other software the person has running. I just checked my task manager and I currently have more than 100 processes running.
Images will bloat a file size.
Docx or doc file, the latter will usually be larger.
Perhaps as important, for a Word file with a lot of text, is whether the file is formatted using Styles. Here is my report of a test done about five years ago:
"I just had occasion to edit a 100-page document that was created without using styles. It was formatted completely with direct formatting. Each page ended with a page break.
"Each time it had to be saved, the save took more than 60 seconds, during which time Word was frozen.
"A similar-sized document formatted using Styles takes less than 3 seconds for me to save. When a page break must be forced, instead of using a manual page break, the paragraph to begin the new page is formatted using a style that has "page break before" paragraph formatting.
"This difference was due entirely to the document being directly formatted - a much higher level of complexity. Each paragraph mark in a directly-formatted paragraph carries with it up to fifty different formatting commands. When formatted using a style, that paragraph mark will carry with it one command - use this style!"
Understanding Styles in Microsoft Word