x870e Hero/ 9800x3d RAM recommendations

Hi I'm switching from Intel 13900k and wanted some DDR5 recommendations..I see AMD expo ram is slightly different to Intel in terms of speeds so....

If the motherboard can do 8000mhz+ What RAM is best? Some are saying default low CL 6000Mhz is better than 8000 kits which I don't see anywhere anyway.

Is low CL 8000 available? Or is it a case of picking up 6000/low CL and overvlocking that higher speed?

I'm not even sure how high you can push 6000MHz ram on the Hero.

What would the top ram kits be right now for AMD expo. Price isn't a big issue.

One last question....64gb kits (2x 32gb) don't seem very common, why is that?