PSU for new rig, is single rail acceptable?

[Biggilus]

Hi hi, I'm finalising the pieces for my new setup which will be a 7800x3d, 6800xt, 32gb DDR5 on a B650 board. No idea how to calculate what wattage is needed but thought I'd go for at least 850W as I intend to replace the GPU in 18ish months time with whatever is capable of 4k 144fps at the time (if one exists). That being said I also looked at 1000W units as they would be more efficient right? Assuming the system draws, say 600W, having the draw around 50-60% capacity is most efficient?
I kind of want a white PSU as the case (Lian Li Lancool Iii) and AIO will all be white. The corsair RM850 is white but also single rail - is that an issue? I was under the impression multiple rails were needed for different power consumption components.

Any other recommendation for a PSU? Not read up about ATX 3.0 but is that recommended more? I would prefer a decent unit over the white aesthetic if I had to choose too, but would rather have a decent white one if that exists.

Primary (well only) use will be gaming including triple As.

 

[Tetras]

That being said I also looked at 1000W units as they would be more efficient right? Assuming the system draws, say 600W, having the draw around 50-60% capacity is most efficient?

It doesn't matter that much, anything between around 25-90% is in the region of 90-93 with a gold PSU. Where they're bad is less than 100 watt, especially under 10%.

The corsair RM850 is white but also single rail - is that an issue? I was under the impression multiple rails were needed for different power consumption components.

No, having a multi-rail config is more likely to trip your PSU nowadays than be useful.

Not read up about ATX 3.0 but is that recommended more?

They're supposed to be designed to handle the spikes of modern GPUs so I'd tend to trust them a little more when they're borderline (for the wattage), but I've never seen any tests that prove it either way. PCIE 5 means you get a native 12/16 pin for nvidia cards, but you get adapters in the box for 8 pins and you can buy a 12/16 pin modular cable for most popular PSU brands.

No idea how to calculate what wattage is needed but thought I'd go for at least 850W as I intend to replace the GPU in 18ish months time with whatever is capable of 4k 144fps at the time (if one exists).

Wattage is far less important than the ability to handle the spikes really, but according to TPU's results, you can expect around 50 watts in games for the X3D and 300 (or less) for an uncapped 6800 XT in games. I'd add 50 watts for the RAM and SSDs, so I think 400 would be a safe estimate.

 

[Biggilus]

Once again thanks!

I'll check out the 3.0s today, but may end up with the single rail RM850