I've got one 1070, one 2070 Super and just recieved a 3060.
Is is possible to mine with all three in the same rig?
And is it good enough having one 750 W PSU?
My 1070 is doing around 140 Watts and 2070 S is around 120 watts.
I don't see why running the cards together wouldn't work. But you're gonna want another PSU for that beast. If you want, get a server PSU/breakout board. They're pretty cheap and you can run about 1200W on them, so great room to expand if you got the PCIE slots