Hey,
not sure if it is already answered for your case, since the supply really seems to have enough connectors....
The point I want to mention: A 3080 can have some significant power spikes.
My Card had a maximum Spike of almost 450W at my tests. This was for less than a seconds, sure,
but ... 750W can be close depends on the cart and other system components
(Maybe not thermal wise but peak overcurrent protection wise)
To make sure; I am quite sure it will work for 99% of the cases quite fine. But on benchmark loads the power consumption really seem to need 2x8 pin.