A high loft poly batting will never 'drape' like a thin cotton batting would. But it makes wonderful fluffy quilts.
You can join batting pieces together. I join them by hand with a large zigzag stitch. There is an iron-on tape to join batting, but I would not use it on poly - it might melt.
Tying is the best for high loft batting, but I have done SITD by machine and it did work.