Yes. Both themes are responsive and adapt to phones and tablets, but the free Focus theme is designed to be used as-is: apart from the mobile menu colors and the mobile logo, it has no separate mobile settings, so spacing and text sizes on small screens follow the desktop values automatically.
Focus Plus adds mobile-specific controls in Global theme styles: a mobile font size for every heading level under Typography, a mobile vertical spacing between sections under Spacing, a mobile padding for forms and mobile title sizes for blog pages. Most modules also have their own mobile fields, such as a mobile font size and line height for titles and texts, a mobile padding, a mobile height for sliders and galleries, and options to hide an image on mobile. These let you fix spacing and text placement on small screens without touching the desktop layout.
You can see the full list of differences on the comparison page.