Is the GS truly cramped inside now? How would it fit someone about 5"7' (my height )? Is the rear able to sit 3 adults or 3 kids?

 

I am 5' 9", no prob really. It is a little small, however that is my perspective after living in a massive GX. Anyway, I don't find that a big problem at all. However, the back seat can only fit 2 adults comfortable (or kids). There are two indentations which almost says "only put 2 back here" I would think the center is suitable for quick drives with kids maybe but not real comfortable for 3 adults.

3 kids sounds fine space-wise, but like I said, the center seat is not conformed to fit someone well.