GBDesu

I have a ASUS ROG Swift PG279Q and I would highly recommend it. It has 27" display, 2k res, and 165 hz refresh rate with great colors. With the rest of the money in your monitor budget, I would recommend getting a VEGA monitor stand on Amazon somewhere since the stand that comes out of the box I found a bit bulky. This one doesn't have RGB though, in case that matters at all.
 
Keyboard-wise, what's important for you? Multimedia keys, clicky or silent, numpad, etc. There is a wide selection of keyboards so you might want to be more specific on the peripherals.

If you're not going to overclock it, there is no reason to buy an aftermarket cooler. Stock cooler that comes with it will do the job just fine, and it also got some decent RGB.

It's all really about personal preference at this point. Do you want that larger curved display or are you fine with working on an already decently-sized flat monitor? The 3 month warranty seems like an already good enough time frame to see if the monitor is functional and up to standard, although in the long-run it might not last as much as it is refurbished.
 
I would personally go for the 27" Dell monitor. It's brand new first of all and it has a much longer warranty with a good enough display to last a couple of years down the road. If you are someone who also likes to buy products with good money to performance ratio, I would buy the Dell.

I would love to do a custom loop, but without any experience doing any intricate water-cooling I'm afraid I'll bust my motherboard with leakage. It's a shame that there are no easy water-cooling aio methods for people like me out in the pc part marketplace. I was also looking at the corsair H115i platinum that claim it fits a TR4 socket. Whats your input on that? 

It's Gigabytes own solution for file transfers and control between desktop and mobile https://www.gigabyte.com/FileUpload/global/Microsite/369/images/networking.html
 
If you don't need such, you can uninstall it.