Laura,
I use some of my small quilts as wall hangings or table toppers or just decoration on a back of a chair. I also need them as examples for my workshops. The smaller quilts are my first wholecloths, now I prefer to make bigger ones. My favourite size is ca. 75"x75".
My favourite thread is YLI. It is already coated so I don't use wax or Thread Haven. I made the same experience with the Mettler thread like you - it tangles a lot and the fraying was really bad. I also used Gütermann several times when the YLI brand did not offer the color I wanted to have.
I'm always very pleased to answer your questions here on the board - the interest in hand quilting is still alive and I am really happy with that! :-)