How to Set Subtitle Font Size
Soft subtitles cannot be resized and are controlled by the player. Hard subtitles can be adjusted by modifying the Hard Subtitle Font Pixel
size in Menu--Tools/Options-Advanced Options, with a default of 14.
Controlling the Number of Characters per Line in Subtitles
By default, CJK (Chinese, Japanese, Korean) subtitles display 30 characters per line, while other languages show 60 characters per line. You can adjust this by changing the CJK Subtitle Characters per Line
and Other Language Subtitle Characters per Line
settings in Menu--Tools/Options-Advanced Options.