I need to check my final word including bibliography and notes. I've tried \quickwordcount and the built-in plugin that overleaf comes but I'm just getting the words of the main.tex excluding the .bib file. Is there any package that counts main.tex and .bib separately?
As others have said "What is a word?". Is a hyphenated word one or two? Is an equation a word or is each symbol in the equation a word? Is an illustration a word? And so on.
In my experience most requests for number-of-words relate to how much space (pages) will be required for printing. Book typographers typically count number-of-words by counting the "words" on a typical page and then multiply by the number of pages. Of course you may have several typical pages, like the ToC, the main text, the Bibliography and so on. But these can be dealt with individually and summed at the end.