documentclass[english, fontsize=14pt, parskip=full, usegeometry]{scrartcl}
usepackage{babel}
usepackage{fontspec}
usepackage{roboto-mono}
usepackage[sfdefault]{FiraSans}
%usepackage{ragged2e}
usepackage{blindtext}
usepackage[right=5cm]{geometry}
%frenchspacing
begin{document}
fontspec{FiraSans-Regular.otf}[WordSpace={1,0,0}, PunctuationSpace=0, Kerning=Off,
OpticalSize=0]

blindtext

ttfamily{}
fontspec{RobotoMono-Regular.otf}[WordSpace={.5,0,0}, PunctuationSpace=0,
%OpticalSize=0
]

%fontspec{RobotoMono-Regular.otf}
blindtext

fontspec{RobotoMono-Regular.otf}[WordSpace={.5,0,0}, PunctuationSpace=0,
OpticalSize=0
]
%begin{RaggedRight}
  blindtext{}
%end{RaggedRight}

end{document}