What are some alternatives?
When comparing Word Online and Overleaf, you can also consider the following products
Apache OpenOffice Writer - Open-source word processor of the Apache OpenOffice suite.
LyX - LyX is a document processor.
LibreOffice - Writer - Open-source cross-platform word processor.
TeXstudio - TeXstudio is an integrated environment for writing LaTeX documents.
Google Drive - Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.
Texmaker - Texmaker, free cross-platform latex editor