New Project Corsair 900R - water cooling dual loop

Sounds like you have more radiators than you need...not saying you can't or shouldn't, but you're beyond the point of diminishing returns, there.

The questions you are asking really cannot be told to you by anyone - we can offer suggestions, but really you should be making these choices. How would you know who was actually giving you good advice or who was not and you decided to take one of them seriously and purchase what they suggest?

Have you read through the watercooling sticky? What info have you come across or picked up so far? What ideas do you currently have?

A 480 rad for a CPU only might be a tad overkill, but it really depends on how much you have it overclocked. Either way, that setup would be fine and you shouldn't have any cooling concerns with those two (very large) radiators.

Those reservoirs look like cylinder reservoirs with D5's at the bottom...is that your plan for the loop? You could also run DDC pumps as well. Just take into account that even in the most detailed schematics, you need to ensure you have enough room in the case for all components. What looks good on paper (or a screen) often needs to be re-evaluated when it comes to actual hardware size and tubing needs. Watercooling takes up a decent amount of space.

I am a fan of EK GPU blocks (full cover) - they are very well built and designed. I know others also like Alphacool and Aquacomputer. I ran 2x Swiftech MCw80/82's for quite a while (universal) and they were very high flow blocks, but most universals are...you just have to account for VRM, vRAM and Mosfets on the PCB - these need cooling also...this is very important.

I also like EK CPU blocks, but I'm also a fan of the older Swiftech Apogee (built one for a friend of mine). The older XSPC Raystorm was a good block for quite some time - you might have some compatibility issues with newer sockets if there is not a bracket adapter...there might be one, though.

For fittings, I like compression fittings, but for a very long time I used barbs...actually still do. My CPU block is an older D-tek Fuzion v2 and the I/O ports are too close together to use compression fittings because the sleeves that slide over the tubing are too wide...so I use 1/2" barbs and fit 3/8" tubing over them. The rest of my current build is compression fittings. Barbs and compression fittings are both technically barbs - the difference is the tubing retention. Barbs will need a clamp or something to secure tubing over the barb fitting while compression fittings use a threaded sleeve that screws down over the tubing/barb to secure it. (see diagram in the watercooling sticky)

For radiators, you have quite a few choices and depending on what speeds of fans you want to run and how much clearance you have will likely determine your radiator thickness. Most manufacturers have thicker rad designs now with some in the 60-80mm thick range in some instances. 35-45mm thick are very common. When you run a radiator with a thicker core, you can effectively run 'less' radiator - for example, a thick 240 rad would compare to a thin 360 radiator when account for good fans and flow rates.

You typically need 2 barbs or compression fittings per piece of equipment - one for inlet, one for outlet. Example - 1 radiator usually needs 2 barbs. 1 CPU block needs 2 barbs. 1 GPU block typically needs 2 barbs, and so on.

Are you getting a universal GPU block or a full-cover block? You only need those additional heatsinks if you're using universal. A full cover block covers all of them and cools them.

If you're using a full cover block, you don't need VRM, vRAM or Mosfet cooling - the block covers all that on a GPU.

You still need good case airflow for components of your motherboard, etc. that require airflow.