How do I open a .docx on a phone without Word?
Open this page on the phone and choose the file from Files or Downloads; it opens in Reading, sized to the screen. Switch to Pages to see how it prints.
Will it look as it does in Word?
On Pages, yes: the layout follows Word’s rules and was measured against Word’s own PDFs, line for line where its fonts are at hand. Reading changes the look on purpose, so that the text is easy to read.
Is it safe to open a document from someone I do not know?
Macros are named and never run, links and embedded files are listed but never followed or opened, and a picture linked from the web is not fetched. The document is read by this page and goes nowhere.