If you're using a very high resolution screen (perhaps a 4k or a QHD panel), you may notice that Windows 10 looks really "small" at the default scaling option. To compensate for the huge number of pixels available on high-end displays, there are DPI scaling options which you can adjust to normalise the view.
This will adjust the text and interface size in most apps, so they appear a more user-friendly size on your display. Some older applications may be problematic and have rendering glitches, but most modern applications will be compatible.
To begin, right click the desktop and select Display Settings:
Then, scroll down to find the drop-down box labelled Change the size of text, apps and other items. You can adjust this to increase the scaling on high-res monitors. For example, on a QHD display you may wish to increase the scaling to 200%. Windows 10 will recommend a setting based on your resolution, which may be a good starting point:
If you have more specific requirements, you can click the Custom Scaling box to enter a specific percentage of scaling.