My first crack at custom loop. It took a while, and the process itself isn't particularly pleasant, but I'm super happy with the result and glad I went through with it.

tl;dr: The process is a bit painful, the performance improvements don't justify the price, but you make something that looks insanely cool and seems inherently a bit nuts (500ml of water gushing thru my 3080?), and that made it worth it.

Challenges/tips

Space

All the bloggers out there are right that the NZXT H510 is not a great case for building custom loop. Throw in a 3080 that, with its stock air cooler, is incredibly long, and you've got yourself a challenge. I ended up learning a bit of 3D modeling to give me ~75% confidence that I chose pieces that fit. Ultimately, it still felt like I had to YOLO buy a lot of stuff and hope I didn't screw up (which, I did, a little bit). Some tips I can share here:
- Swapping the graphics card's air cooler for a water block drastically shortens its length, which is very important. EKWB gives very clear measurements on each of its components on their product pages. Obviously, use those.
- To save horizontal space, I put the fans on the other side of the case's front radiator mounting frame. This put the fans pretty close to the front of the case, which surely isn't the best for temps. However, everything runs fine (sub 65 celsius for CPU/GPU under gaming loads).
- For mounting the res, I ended up using the EK-UNI Pump Bracket Vertical to mount the pump/res off of the radiator. It was incredibly challenging figuring out what pump/res to get and how to mount it. Once I realized, tho, that the graphics card block shortens the length significantly, choices became much easier. I specifically chose the DDC (not D5) EK pump/res because it would protrude out less than the D5 version. This ended up proving critical, as it gave me enough space to fit the 90-degree fitting and ball valve to one of the plugs at the bottom of the pump/res.
- Be wary of the configurator tool on EKWB's website. It originally told me that the 280mm CoolStream radiator would fit in my case, and it simply did not. I had to go through a somewhat painful customer service experience to convince them to do the exchange for the 240mm CoolStream. Eventually, tho, they conceded, and picked up the 280mm radiator and its fans free of charge. I do, however, highly recommend talking to their customer support before you order - they were quite helpful for the questions I had.

Fittings

- There are a lot of different sizes to keep track of in this process. Fittings sizes, tube sizes, rad size, fan size. I probably could have posted something on reddit saying "hey, here's what I'm going to order, does it pass yall's sniff test?", because...
- Shipping from EK will cost you money and time. I ended up not realizing I needed an extra fitting and a fitting adapter (for connecting the ball valve), and I paid marked up prices from Titan Rig to get them promptly.

RGB

Things are less configurable than I thought. I use Aura Sync, and via Aura Creator messed around with creating some cool RGB profiles.

My mobo has a single ARGB header, 2 RGB headers, and some RGB RAM. That ends up showing up as 3 total devices in Aura Creator (and Armoury Crate) that can be individually customized: 1) ARGB header, 2) RGB headers (which both show up as a single device), and 3) RAM. I was a bit disappointed that I could not independently configure the colours on each RGB device I had connected.

Filling it up!
- Definitely get a leak tester. I had several leaks in mine, and knowing that I could debug these with air instead of water gave me the ultimate piece of mind. It was still hard to find each leak - I ended up using the good ol' soapy water trick (with well placed towels protecting things) to help me locate the leaks. Once they were all fixed, and I could see that my loop could hold air pressure for hours, I felt totally comfortable putting the water in.