Below is what I suggested to someone else...
The SN550 has had parts downgraded, but of course it's the cheapest, then you have the MP400, SN750 and then gen4 SN850. I personally have a SN850, and am hoping this will make a difference in the future. I'm fully aware at the mo just for game load etc, no it doesn't, but if I'm forking out, I thought, this is the most futureproof I can go, and at mo, OCuk has a discount so £139 is actually a very good price..other sites have it for £190 odd...it's the same read/write as the Sammy 980 Pro at over £200 and firecuda 530 at £190
I went B550 board as only wanted one gen4 and at the time X570 boards were all way over £200. If want multiple gen4 though, it's the way to go, and the x570 tomahawk has everything you need.
I'm not up to speed on the use on multiple nvme and sata at the same time, as know on some boards sata 5/6 get disabled etc, so would need to look into it..but that comes down to budget also. @EsaT generally is though, he m ight be able to point you in right direction. I'll try have a look but going to be tied up for a few hours from now
Same goes for Ram, I've got 32gb 3600c18...(just put flight sim on with flyby everest...got to 12.6GB ram in use, with this web page and 6 other tabs open in background, so 16 will do, but as I built, don't want to have to buy more in future, and 2x16 cheaper than 2x8 on a per gb price at mo..it was a lot cheaper than the 3600C16 and yes, prob loosing a few fps, but I'm not unduely bothered...3600C16 will be faster, and in 2x8gb not much in it, 2x16, it's costing well over 10% more than the c18 for 1-3% gain..guessing with that case, rgb not a factor
It's a monster
def shop around though..some large variations between retailers, and even taking shipping costs, you can save a lot by sourcing multiple locations
Put in the X570 tomahawk in there also as has wifi 6 and with discount better than the B550 boards with wifi atm..plus both nvme's are gen4 compatible. With Win11 and direct storage coming in to play will be interesting to see how the faster nvme's perform. The corsair MP400 is on offer and sits between the sn550/sn750 for read/write performance, and the SN850 right at the top end for gen4 performance atm and on offer@£139. Both air coolers more than capable for the ryzen cpu, the Artic may go well with the case, the brocken a smidge cheaper, also slightly offset to give room for the ram sticks..a 2nd fan can also be added to increase airflow..went non rgb
My basket at Overclockers UK:
Total: £1,171.96 (includes shipping: £11.10)
) so I've gone for it and will be taking the middle B550 path after all.