The "out of the box" font setting for Delphi 10 Seattle is Segoe UI with a font size of 10. I prefer a font size of 9. Embarcadero has a nice wiki on how to change the initial settings.
http://docwiki.embarcadero.com/RADStudio/Seattle/en/System_Registry_Keys_for_IDE_Visual_Settings
I made one minor adjustment to EMBT's recommended settings:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Embarcadero\BDS\17.0\ModernTheme]
"FontName"="Segoe UI"
"FontSize"=dword:00000009
"MainToolBarColor"="clGradientActiveCaption"
The only other tweak I made was to the editor font. I prefer "Consolas" mainly because it formats zeros with a slash which makes them stand out from the letter "O". The editor font is located here:Tools > Options > Editor Options > Display
Share your "out of the box" tweaks for Delphi 10 Seattle in the comments.
Enjoy - Semper Fi
Gunny Mike