What research? The ideal number of characters for what use? I suppose that research could be done for reading. on Wikipedia, you're more likely to scan the text to actually read it word by word. Sure, there are some articles on Wiki, you'd like to read as a whole. But they've got people. People who've done their homework. If you did your research, you'd find that Wiki community already did research on this matter and put it up to vote. Due to mixed results of the research, they decided to stay with the current layout.

Also, there's this thing called the speed of reading. If you have to switch line every 70–90 characters, you have a bigger probability of getting lost and the reading speed will be slower as well. I don't know if you noticed but if you put Wikipedia article and Medium article with the same content right next to each other, Wikipedia would be much quicker to read.

The lines of this are much more blurred than you let your readers believe in your article. If there's some research, attribute the authors of the research, share their work. Studies they did, documents they wrote.

The text size, line length, and other typographic factors should be decided by an experienced typographer. There's no such a thing as “one way to rule them all”. What's makes a good designer is to always know there are other ways to do the job and to try them. Not just to say that this way is right and this way is wrong. If it would be that way than anyone could be a designer after just reading few articles. But that's not the case. Being a good designer requires a mindset.

These “UX” articles are madness. There's always seems to be very little of research behind them.