most of mine is 50 weight..i thought most hand quilting thread was 40, but since i don't hand sew..i don't know for sure.
I use gutterman cotton(from Joanns), or masterpiece, superior,king tut.. bottom line. my machine is not picky about threads..so i can use just about anything.
i have always heard, piece with cotton, and quilt with whatever your heart desires! I am in love with verigated threads! i have used clear,Emb threads, glow in the dark..
google
"redrock threads"
or
"superior threads"..
you will find all sorts of helpful info there!