I use a pretty fine needle, usually I piece with a 10. For most of my quilting career I was happy with my vintage machine and Dual Duty thread. In the last couple of years I've been using finer threads, usually now I'm using Sew Fine both top and bottom. Also, tiny stitch length -- I'd say no less than 12 per inch. My Bernina turns on at 2.5 -- I'm not sure but think that is about 10 per inch and would be fine for garment construction but not so much when cutting stitches in modern strip piecing techniques. I'm usually piecing about 1.85-1.9, not sure what that translates to 12-16??
Also, as b.zang says, handle your strips gently. If I have a top that has a lot of seams (or before a plain outer border), I will often stay stitch the pieced section within the 1/4" seam allowance, maybe using a slightly large stitch than my piecing, so say a 2.