Menu Size

Sour's menus, Minecraft's GUI scale and the HUD are three separate sizes.

Display
Menu scale is the first row on the Settings page.
Menu scale is the first row on the Settings page.
To changeUse
Sour's menus (Mods, Settings, Cosmetics, the title and Esc menus)Menu Scale, or Set Per Menu for one menu at a time.
Text in Sour's menusUI Font Size
Minecraft's own GUI (hotbar, inventory, chat)Options, Video Settings, GUI Scale.
One HUD widgetIts own Scale setting, under Layout.

See menu size, fonts and looks.