Microsoft Office doesn't run on Linux, nor does Visio - so use Inkscape. It's a vector drawing tool like Adobe Illustrator. It's pretty basic, but you can do whatever is necessary for quick drawings easily. It just takes a little practice. The connector tool is important to use vs. just drawing lines.

It is possible to use OpenOffice or LibreOffice, but the package is pretty big and the file formats are marginally compatible with Microsoft Office. Inkscape generates .svg files, which are basically sophisticated XML files. It can export to PNG, which is the best format to use, or JPEG and a few others. You can view a .svg file with any browser, it's not as easy with Visio, Word or Powerpoint.