the vw property will scale the font to the size of the View-port Width
vh will do view-port height but i really wouldn’t use it on font’s.
I find using the vw for font’s is a real pain and takes too many media queries to get it looking right. because as you will see, a font taking up 5vw or whatever, can look awful with just a small adjustment to the width of the view-port. For me, at 1920px wide - the font overflows the box and demonstrates this issue, but at a smaller width the font becomes too small.
Maybe its me just not doing it right but i find it easier just to use non reactive font sizes like px or the preferred rem unit.
I just change the font size by using rem when the design dictates. this way I find there isn’t too much messing about and i can change the size as needed with existing media queries that I might have…
If you want to delve into responsive typography a google search brings up plenty of articles - too many to link to!