Alphyte

I will recommend the Leopold FC980M or FC900R for your needs. Those 2 keyboards are extremely well built, with 1.5mm doubleshot PBT keycaps, as well as dampening foam in the case and a nice, moderately thick PBT chassis.

It is a gaming CPU, but you are unlikely to make it perform better than the 9700K or 8700K unless you spend a few hundred bucks on a custom loop or something

Even if you are streaming, I wouldn't use CPU encoding on any non HEDT CPU period. Turing NVENC is better than x264 fast and x264 medium will just cripple your performance.

#1. You definitely do NOT need a 9900K for gaming. 
#2. If you can, I'd go 8700K or 9700K with a 2080 ti over your 2 options
#3. For the 2700X, the X470 Gaming Plus/Pro are decent choices for decently cheap.

#1. You definitely do NOT need a 9900K for gaming. 
#2. If you can, I'd go 8700K or 9700K with a 2080 ti over your 2 options
#3. For the 2700X, the X470 Gaming Plus/Pro are decent choices for decently cheap.

@Mr.Sniff Yes, Bitfenix.

Also:
 
I wouldn't recommend P350X as H500 is the same price and performs better
I would still recommend a Formula over a MWE Gold. Same efficiency != same quality

If you are just gaming, go for a 2600. Also, I would change the case to a Meshify C for that price, as well as the PSU to a Formula Gold. Other than that, I'd say it's fine.

While tripleshot keycaps are a thing, I can see little probability of this happening with the design you mentioned. Tripleshot requires even more money than doubleshot, and all the tripleshot caps I know of aren't RGB at all. This also requires a completely different LED design, which is also not very feasible IMO.

I will recommend the Leopold FC980M or FC900R for your needs. Those 2 keyboards are extremely well built, with 1.5mm doubleshot PBT keycaps, as well as dampening foam in the case and a nice, moderately thick PBT chassis.

@ImAyaanKhan
 
Ducky has been a bit overhyped due to the tfue thing, but they are far superior to most other RGB keyboards, including the K95 RGB Platinum you recommended. The Ducky has overall better quality with its keycaps, build, and stabilizers being overall better. That being said, if you didn't need RGB, I would recommend either the FC980M or the FC900R as they are EXTREMELY good for the price and pretty amazing overall. 

There isn't one "best keyboard" for anything. It all comes down to personal preference. I used to game on switches with hysteresis completely fine. I would say that most mainstream boards from gamer brands are far from great. I personally would recommend Ducky if you were looking for RGB, or Leopold if you wanted to sacrifice RGB for that extra bit of quality.

As long as the settings are not detrimental, no.

Again: Don't care about your history, just pointing it out.

There really is not a single point changing the PSU. Maybe 650W would bring you closer to that "50% best efficiency" crap, and is a bit safer in case of a short, your power bill is literally almost unaffected by it, and your chances of your PSU shorting are astronomically low.

#4.Response time 1ms/2ms and so on is useless as there are no standardization for it. 5ms monitor could perform equal or faster than 1ms monitor from different manufacturer

For Streaming, I wouldn't stream with CPU, on any mainstream processor right now. Turing NVENC will be superior to CPU encoding unless you want to cripple your performance, as detailed in this video.

@LukeSavenije that link is for a G1+, which is highly improved compared to the G1. G1 is pretty trash, but G1+ is decent from what I've seen.

@Jr SavageZGet the ones I or @JM21 listed, and you'll be completely fine. TXM is a bit on the low end for a gold PSU though. Again: when you have that sort of build, I would 100% go for a high quality PSU.

Just know that oversizing your power supply isn't going to draw more wattage from the wall. The PSU will only draw what it needs up to the rated amount.

There really is not a single point changing the PSU. Maybe 650W would bring you closer to that "50% best efficiency" crap, and is a bit safer in case of a short, your power bill is literally almost unaffected by it, and your chances of your PSU shorting are astronomically low.