Ahh I dont think your board has BIOS flashback, Asus seems to only do it on ROG and X series boards unfortunately
Double check but I think I'm right. You probably have to pick up a 10100 and sell it on if you want to flash to the latest.
I think 6/12 is about right for gaming right now, any less is not as future proof, and if you're doing some video stuff you might benefit from an 8 core more as you say.
The 11400F and 11600K seem like the pick of the 11 series for price performance, better than AMD currently I think. 11700 is obviously a bit more powerful and faster but uses a lot of power(heat) and costs a lot more
For an Intel 6 core and up I'd suggest a big dual tower air cooler if your case has room for it, or a 240/280mm AIO. They all cool roughly the same at the end of the day especially if you're not overclocking to the bleeding edge.
There's several big air coolers that are about the same, Noctua NHD-15 and NHD-15S, Deepcool Assassin III, Cryorig R1 Ultimate/Universal, and some others, and a million 240/280mm AIO's. The only thing with some air coolers, you might have to be careful if you have tall RAM or if your PCI-E slot is little close to the CPU slot. The NHD-15S does solve this by being offset to the upside and losing the front fan.
Of course AIO's dont have those kind of issues at all, but they also need replacing every few years where air coolers will go basically forever I'd personally go for whichever was quietest these days. Whatever floats your boat.