I do 99% of my quilting with a Schmetz 75/11 quilting needle, and either 40wt or 50wt cotton thread.
Tension should be checked for every project, as different fabrics, battings and threads all change things... sometimes even a color change of the same thread will cause the tension to need to be adjusted!
Make certain you're not moving the fabric too fast, this along with improper tension, can cause loopies on the back.