Successful mods for both -

1. For second armhole edging, pick up four stitches from first edging rather than cast on four more and seam them together. This saves a seam and looks neater.
2. Keep all three pieces on needles and do a three needle bindoff all the way across the top. Looks neat; saves seaming.

On example 2 (yellow) I omitted the slip stitch edge because I felt it didn’t allow enough “give” the the front edges. However, I’m not sure omitting it improved that, so next time, I’d do the slip stitch edge again. It just looks more polished.