I dunno what a PI is, but my honours thesis supervisor was the person who first introduced me to TeX. And gods, I wish I had known about it earlier in uni, or even back in high school. It is so useful when writing any sort of papers with sections and diagrams and bibliography.
Then start writing in Markdown. Markdown is easier in syntax, supports LaTeX equations, has metadata and is in plain text so you can use git. And the killer feature is you can use pandoc to convert the markdown file into word, pptx, LaTeX pdfs, html etc. you can also setup a make file that runs pandoc when you ask like this
I also have my reports in latex inside a git repo, complete with a makefile to generate graphs from csv containing simulation results. However I am too ashamed to publish the entire version control to a public repo
.gitattributes can invoke Word on windows to diff versions, and there are plenty of open source scripts that can do it if you don't have a copy of Word (or Windows) lying around.
But Word is like shit for papers. Use LaTeX instead.