It has been my experience that seat struts do transfer weight to their respective corner. I have not heard of them preventing weight transfer. And when a seat strut has broke, my drivers notice the lack of transfer.
Same story for the weight up high. It changes the center of gravity and tends to help the kart “lean” more in the turns (transfer weight), which is especially helpful when your driver is small. Now, if your driver is more normal sized or taller, I definitely would not put the weight high on the seat; rather, I’d put it as low as possible.
