I have a 4090 in my Ryzen 7700X system and a power meter; 850W is overkill for a 4090. My system never uses more than 650w. What’s more important than the power rating is buying a high-tier PSU with good overcurrent protection, cause the 4090 tends to have power spikes even a good 750w PSU should be able to handle.

If you bought a PSU certified for PCIe 5, then you’re most likely fine. If you didn’t have to use a squid adapter to plug in your GPU, then you’re more than likely good to go so long as you didn’t buy a shit tier PSU.