you can use till 8000 with over clocking (preaty easy in Bios)

So I'm not sure I can answer all your questions but I can tell you that I have a motherboard with 4 Corsair Dominator 32gb ram strips per ram that go to 6000mhz and I can tell you that the motherboard supports them with almost impossible ease. almost impossible, and the motherboard is made to support up to 6400mhz so do not worry on this point but as you know having so much it is useless but if you want so much for the future is a very good idea.

This does not necessarily have much to do with the board, but rather with the memory controller in the CPU. Basically, however, it is more difficult to overclock 4 bars than 2 bars. For this reason, I would rather recommend using 2 bars.

Furthermore, the "sweet spot" for Ryzen 7000 seems to be at fast 6000Mt/s RAM. As soon as the Frequen is above 3000MHz (=6000Mt/s) the CPU switches the UCLK frequency from 1:1, i.e. 3000MHz, to 1:2, i.e. at 6200Mt/s (3100MHz) to 1525MHz. You can go back to 1:1 manually, but the probability that the CPU can achieve this decreases. 64000Mt/s, i.e. 3200MHz UCLK is maintained by few CPUs.

It seems to make the most sense to get good 6000Mt/s RAM (e.g. G.Skill Z5 Neo 6000CL30) and then tweak the timings on it, most easily with Buildzoids timings for Hynix A-Die (which the G.Skill 6000CL30 use exclusively, the 6000CL32 apparently use M-Die). Most kits should be able to run these timings. (https://www.youtube.com/watch)

See also Hardware Unboxed, which tested various timings plus 6400Mt/s RAM:
https://www.youtube.com/watch

As well as Igor's Lab: https://www.igorslab.de/amd-ryzen-...

4 DIMM modules, max. 192 GB, DDR5 8,000+(OC)/7,800(OC)/7600(OC)/7200(OC)/7000(OC)/6800(OC)/6600(OC)/6400(OC)/ 6200(OC)/ 6000 (OC)/5800(OC)/ 5600(OC)/ 5400(OC)/ 5200/ 5000/ 4800 MeECC and non-ECC memory, unbuffered* Dual channel memory architectureSupports AMD EXTended profiles for overclocking (EXPO™)OptiMem
II
* Supported memory types, data rate (speed) and number of DRAM modules vary depending on processor and memory configuration. For more information, see https://www.asus.com for the memory support list.
* Non-ECC and unbuffered DDR5 memory supports the On-Die ECC function.