It depends on which browser you are using. Google knows...

- iOS https://www.groovypost.com/howto/change-a-websites-text-size-on-iphone/
- Android https://support.google.com/chrome/answer/96810?hl=en&co=GENIE.Platform%3DAndroid 

I am using SN as PWA not using browser so how do you adjust? 

 works really well... and mobile browsers allow font resizing for improved accessibility as well.

Design

Is the SN text in mobile view small, or is it just me?

why? `ctrl +`/`ctrl -` works really well... and mobile browsers allow font resizing for improved accessibility as well.