It would be helpful if you could post a picture or a link. I feel like I would offer the wrong suggestions otherwise.

I think it was Jo Morton who clipped all her seams. I have done it myself when necessary and it does make everything lie flatter for quilting. Maybe it's too late to press all the seams open but if not that's definitely a good option too.

I don't know the quilt, but based on your description I'd say you have several options. I've started pressing my seams open a lot more now because you get a much flatter quilt top and it's nicer to quilt. So that's something you could do. You can't nest the seams when they are pressed open, but I find that you can still feel when they are in the right place and I always pin, so I get nice intersections even with the open seams.

Another thing you could do is what I think you're suggesting, which is to clip the seam allowance in places where you need to change the direction of the seam. I've done this once or twice, but not often. There was a guest on one of the shows (don't remember who or which show) who does this all the time, so it shouldn't hurt the integrity of your quilt.

I'm not a new quilter but have run into a problem while putting the blocks for Snapshot together. Each block has a sash running though the middle of the same fabric so when joining to be able to match perfectly, the seams need to goin in opposite directions to nest. The blocks are all assembled with many seems and ironed beautifully but need to be twisted at intersection to fit! Does anyone have a suggestion? I was wondering if I could snip each seam a bit to press flatter. The front looks amazing, the back a twisted nightmare! Quilting will be challenging?