1. for blurry texts - go to Project Settings -> toggle the advanced settings button on the top right -> search 'MSDF' -> go to 'GUI > theme' -> Check the checkbox that says 'Default Font Multichannel Signed Distance Field' -> reload project. this will make text clear. you'll have to do this for every new project.
2. window size issue- Before exporting the project, go to Project Settings -> Display -> Window -> put stretch mode as 'canvas item' -> and aspect as 'keep' (you can play around with aspect, but keep usually works best).