I would recommend Primary.
it’s easy on the eyes. bold and italics are different colors which makes them stand out more. which in turn makes the information in the note easier to parse depending on how you format/write them. you can use the Style Settings plugin to adjust the look. i’d suggest changing the Header Colors to the “primary colors” option, because it breaks up the wall of text a bit more, which again makes the information easier to parse. also the icons and everything look good. none of the interface features get hidden/removed. and its actively maintained.
a close second would be the LYT Mode theme. the colors are a little less easy on the eyes IMO but its still a pretty good theme.