Ichi

NR400 no doubt.

Take noise into consideration. If you push the Strix fan to 37dBa which is what the SC2 is running at then yes it will run cooler than that. GPU boost is a thing, the cards won't run at exactly the boost clock the box says, it will run alot higher if temps allow it to. Manual OC is always the best thing to do anyway if you don't mind spending the time to find the sweet spot for your card.

It is called snow.

Air cooler is not an option? It will last you basically forever compared to AIO which have lots of points of failure.

No space for a 240 rad? I wont recommend anything smaller for AIO. For that price an air cooler could actually perform better.

The airflow is disappointing... Anything you put inside will run hot coz of that solid front panel restricting the 200mm fans... It's a shame really, hope they make a revision of it to put mesh front instead, it does look great based on Steve's HAF-IFY video.

How about the CPU? Load temps? Adequate cooling for the OC?

Keyboard would be old generic Dell membrane. Had it for a good 4 years or so before changing to MKB. Ever since then nothing dies on me, I usually sell it off and get a new one every so often to try different switch/brand. Currently on Ducky Shine 5. For 'gaming' mouse, had a Logitech MX518 for a good 2 years before it dies on me and using Deathadder 2013 since then until now, doesn't have any reason to change it out to anything else so far, been doing great for what I'm using it for.

You need to allocate it if not mistaken. Lots of guide out there if you search for it...

AMD FX 9590 be like IT'S OVER 9000!!

That's actually alot for a build like this, I would say max $700. Depends on location anyway, if it's fair for your location then it's fine.

Yup. Just get the Define S, it is built with watercooling in mind.

Both will be fine as long as you're not doing liquid cooling.

None of those can fit a 360 rad which is what OP wants...

That's painful...