BFV is a light load for the 6900xt so it only uses about 90W but It will jump up to 130W at times and the 5600x is only using about 40W. I wanted an 850W PSU but had to get a 750W corsair which is super efficient at 91%.That's... significantly lower than I planned for (5800X and 6800XT) or read up on. Any reason why it might be that low, even with the undervolting considered? (I mean, even my old 6700K/1070 drew more under load)
Fwiw I went for a Corsair RMX 1000W PSU (over the recommended 850W) just to be absolutely safe and confident, for the above and any upgrades in future given things like PSU or storage should last more than one upgrade of CPU/GPU etc.