What a great graphicI'm all over the place with my personal preference for side stones. I like both of your inspo photos, but I prefer the smaller side stones between those two examples.
I have a 3 stone ring with similar proportions to your three stones and I love it.
I found this graphic earlier when I was looking at pictures:
It's a beautiful ring. It's the physical position of the side stones that add to a balanced symmetry. I vote larger and a similar spacing as this ring.I just had a ring made with DK in very similar sizes - they're cushions, not round, but my center stone is 6x6.5 and the sidestones are 4x4.5. It's on his IG if you want to have a look.