The long and short of it is:
a. stay stitch the seam line unless otherwise directed
b. when putting together two pieces of fabric the correct order is: match notches, match beginning and ending of seams, match in between, clipping the seam allowance if required. Clipping is particularly important if matching curves that do not look the same
Here are some pictures as an example. Here I am using the bodice of Vogue 1350, which I
This was a muslin, so I did the stitching again in that corner without removing the wrong lines.
Match notches, then the end of the seam. You can see here that one of the pattern pieces has a bit more ease. This is FINE! That ease is present between the notch and the seam end, so it SHOULD NOT be distributed anywhere else, since that's where it's needed.
Pin the seam, and clip so the piece that seems "shorter" matches the piece that seems "longer". Note - they're not actually different, the seam lines are the same length. If you do the clipping, then you won't be stretching the fabric.
Stitch (not over pins). In this picture you can see how the clipped fabric actually behaves.
That's pretty much it! It was a really good thing for me to learn just in time for making V1350 as well, since this dress has 4 (yes FOUR) of these really tricky corners.
And here is a sneak peek of the dress itself: