It is never good to use
vmax (or any other unit that is based on the dimensions of the view port) by themselves for the font-size because it prevents the user from manually increasing the text size, which is an accessibility failure. If you want the font size to scale a little with the width of the view port then you need to combine that with a relative font size as well, such as:
font-size: calc(0.8rem + 0.2vw);
This prevents the font size from ever getting below
0.8rem but allows it to grow a little as the width of the browser increases. And the
0.8rem allows the user to manually increase the font size regardless of the width of the browser.
Personally, I almost always just use
rem units for font size, but if I have a really big heading then I might scale down the
rems and add a little
vw so the heading adjusts a little for narrower view ports.