I leave the listing as long as my supplier has stock and I'm able to get them.
As for motherboard, I could put you in contact where I was working and you can talk to them about what you want. I know they had a lot of Gigabyte Aorus boards which would be the most recommended ones.
9700k I got from em is doing 5150 at 1.3 vcore, tops out at 78c in real bench (custom loop). Have not tried lowering vcore or raising clocks, just set it real quick, tested and been great since lol. I should mess with it and see what it will do though since its so easily did 5.15 (set for 51 but doing ~5150).
I have another non delidded 9700k (purchased new) that barely does 5ghz with corsair aio (hits mid to high 80's at 1.28 vcore in real bench).