Its fine. You can do 6400 even. Higher with some luck. Probably not with kit.

Depends on the price. Z690 boards are good quality and tend to cost a lot less. RAM oc is worse on ddr5. For Ddr4 there is no difference.

The ~$90 12100 beats most of them, that is probably why. There is really not much to consider any more. Even if you are looking for high core count cpus for a server or something. You may want to look at first gen threadripper or similar.

for overclocking 24GB hynix M-die dimms are best but they generally cost almost twice of Adie 16GB dimms. It’s easier to hit 7600+ with these, specially on 4 DIMM boards.

There are 24GB dimms from micron on the market as well, those are not good for high speed so watch out what you are buying.

16gb Adie is better value right now, You can get a kit for like $100. Higher capacity dimms are just newer, better and cost more than a over year old Adie. Something better probably comes out next year, it’s a rapidly evolving segment.

It is not 8gb, hurray.