Impact Soundworks showed off a new Kontakt library of an 8 string electric guitar at NAMM 2020, inspired by modern progressive metal bands with technical playing. The library is called Shreddage 3 Hydra.
I got a pretty awesome demo of the library, and I was very impressed at how realistic it could sound. The clean chords and leads were perfectly realistic, but the 'chugs' were also very realistic as well. Typically sample libraries of guitar fall apart when it comes to repetitive strokes on the same note, which is very common on guitar (especially in metal and djent where its pretty common to play a bunch of fast notes on the same string for a large portion of a song). Hydra (and maybe the other Shreddage 3 libraries) had a nice solution for this because theirs a previous note key which makes it very easy to perform riffs like this.
The Shreddage 3 engine which is used in several other libraries is very powerful. It can figure out what fret ranges should be played on the guitar, and you can manually assign certain open strings if you need to. Almost every aspect of the guitar is assigned to keyswitches so you can easily switch preferred strings and articulations. You can assign picking patterns and other performance metrics to decide what style you need for your application.
More info soon!