CraptacularOneWell with a 10850K if you put it in a Z590 board you lose the ability to put a PCIe NVME drive in the top M.2 slot. Just grab a 11700K for the Z590 and benefit from PCIe 4.0 PCIe speeds for M.2 drives.
DEJ915Z490 is going to be more optimised for 10th gen cpu.
bscool2I have/had z490 Apex, Unify, z590 Apex/Hero and used 10th and 11th gen CPUs in them. For best results and easiest compatibility I would use 10th gen with z490. Unless you plan on using a lower clock XMP ram like 3200-3600 then it doesn't matter. But if you want to run 10th gen CPU with 2x16 b die at 4400c16 + on z590 it is hit and miss. Asus is good but I have seen Asrock has issues running 10th gen in z590 over 4000mhz with DR b die. I also had an issue when using 10th gen cpu & SR b die wont run 4533 cr1 in z590 Apex but it can in z490 Apex. The main reason why is they focus on 11th gen CPUs for z590 MB(bios) as that is what most people will run in z590. Also running 11th gen in z490 works but you lose some performance in mem copy speed and latency is a little bit higher vs using z590 MB. Basically if you don't care about memory OC either will be fine.