I had this issue too, I tried changing the color of the text of the subtitles in Notepad and it didn't work for me. The only thing that can change the color/font of the subtitles is going to Windows Settings-->Accessibility-->Captions--> then change "caption style".Also regarding what I previously said about the subtitles not standing out, does anyone happen to know how to change that? i've seen the other videos of his that have been subtitled and they look much better and much more legible.
I think the main reason some subbed flim13 videos look a lot better though, is because they don't use .srt files to subtitle. It's 100% just a text layer in a video editor, which is much more easy to manage anyway.