LibreOffice Writer is compatible with MS Word, but don't expect that every format you applied in Word will be the same if you open the file in Writer and vice versa. No such thing as 100% compatibility.
I have been creating documents with MS Word at work and modifies it at home with LibreOffice Writer, and although they are compatible, there are visible changes in the document's formatting such as spacing, font, header and footer, and yes alignment of images as well.
I'd suggest that if you don't need to open it with Word, stick to the default
.odt file format.
If you do need to access the file with MS Word, then I'd recommended to save it as
.doc and not as
.docx. Saving it in older doc version will guarantee (most of the time) to open it in the original document formatting.
For more assistance, please see How to maintain document compatibility between LibreOffice and other office suites?