I put my Brother SQ9000 at 1.4, but I am thinking that each machine may be different.

I use 2.50 on my
bernina.

I was getting a lot of puckering so I asked my quilt shop about it. They thought 2.0 was too tight and suggested 2.5 or 3.0 I ended up going with a 3.0 for that quilt. I usually use 2.0.

For piecing, my stitch is a little bit smaller than 2.0 on my Bernina. This may be because I prefer to press my seams open.

More likely, though, it's because my very first sewing teacher complimented me on how much thread I had committed to my project. That terrycloth bathrobe still serves me, >35 years later. Of course, had she not insisted that I add lots of "ease" to the pattern, it wouldn't fit me at all these days. What a wise woman!