With the 2x3090s, do you have them connected with the NVLink connector or are they just running over the PCIe lanes?

iirc 3090's doesn't have NVLink, or at least the one I have doesn't/

It must be the one you have, because 3090's were basically the last consumer level card to have nvlink.

https://www.fibermall.com/blog/nvlink-compatible-cards.htm