Font size relative to block size?

Questions
1

I’m producing a flyer to print in various sizes. I’m getting a bit lost on the distinction of ratios, lengths and relatives.

What I want is something like #text(size: 1%) or #text(size: 1%.length) (exact percentage to be figured out experimentally.)

2

Are you looking for layout?

#block(/*width: ..., height: ..., */ layout(size => [
  #set text(size: 1% * size.width)

  #lorem(300)
]))