Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
When you say that your DPI is set at 100%, does that mean you have it set at 96 DPI or is it 120 DPI or higher?
If you click on both the two screen grabs you posted and open them in other tabs, and then toggle back and forth between them you will see the second picture is wider overall. This can be caused by the screen display being set at a number higher than 96 DPI. Pictures are rendered larger, and text remains the same.
If you have your display set at 120, change it to 96 DPi, open and publish your web files at that resolution. You will probably find everything lines up ok.
DavidF