The Italian ones are nice, as are the UK ones (if a bit cramped). The Nightjets mentioned in the article (mostly taken over from DB's CityNightLine a few years ago) are variable; the Poland-Ukraine one is pleasant enough but poorly timed. I had a pretty bad time on a Hungarian Railways one. The Russian Railways ones from Paris and Nice to Moscow have a reputation for luxurious looks but bad (or at least not westerner-friendly) food.
Austrian ÖBB, which runs in multiple countries like most lines going through Germany, is working on modernizing their trains, but they also have quite old cars. Not sure if there is a good site showing car types and train lines.
https://www.nightjet.com/en/komfortkategorien/nightjetzukunf...
That is, "Most Nightjet trains use Comfortline sleeping-cars built by Siemens in 2003-2005 for German Railways' City Night Line sleeper trains." and "Below: Comfortline sleeper layout. All compartments can be sold as a single, double or triple."