For Science!

Hardline tubing any day of the week for me

Sounds good to me.

Either is fine, ports on top means air is easier is bleed, ports on bottom will make the liquid easier to drain for maintenance. Given you have a reservoir somewhere, the air will find its way there over time either way.

While common for aquariums, the PC-space UV lights are purely for aesthetics. We deal with algae and growth by putting in biocides in the coolants (something you can't do in aquariums) and so there is no need for a UV sterilizer for a PC.

Up to you at the end of the day, but it just doesn’t add up in a SFF PC if you just reheat your internals, in an all exhaust setup the negative pressure will mean that the intake air will be the outside air, anyway, so it’s the same, just not reheating the internals.

Nah, its just a different supplier You can check their current partners here: https://www.asetek.com/gamingenthusiasts/diy-partners But it really only looks like the ROG one.

They look really different, "janky-ass chinese" is probably much less janky than anything you can hope to achieve DIY.

For the water temperature it sounds like "normal-to-a-bit-high" range. Making sure the mounting is okay is of course a very sensible thing to do, but if the thermal paste spread is okay, then really I think you are limited by airflow and radiator surface area. One thing is that I am a strong advocate of negative pressure and throwing the heat outside the case especially for small form factor, if that's what you're doing.

How much radiator space are we talking about here?

4.7 GHz is unrealistic without subambient cooling. No amount of liquid cooling (at least conventional water cooling) will get you there. You need to get your expectations in line with reality and stop posting this topic over and over.

Yeah, and even with the best case scenario, they are still pretty ugly imo My only thought with you in particular is that the 5950X is likely the last AM4 CPU, so if AMD releases the next platform, you may need a new CPU block/mounting hardware.

You can stop worrying about it, nickel and copper are fine together. Though its still good to have anti-corrosives in the coolant anyway.

ThermoSiphon cooling, they had a massive cooler prototype that performs well (but it is huge) they claim the production model will be half the size and perform the same, but I have my doubts. https://www.icegiantcooling.com/

I think it's also good to point out that just because it is a custom loop, it is not automagically superior. Custom loop just lets you expand on the available surface area semi-indefinitely, and that's what gives you the performance/silence. The complexity is only in the setting up process, the difficult in "maintaining" it is really a non-factor since you could choose to neglect it, and it will still beat the lifetime of most AIOs. The only reason why you think about the maintenance of a custom loop is because you can maintain it at all, and it is for the good of the system.

Newer pastes on the market will always pop up here and there (there are already ones better than MX-4) and longevity will depend largely on the storage condition. All in all, I would recommend a small amount of high quality paste, as the price per application is not so high anyway even with a small tube of Kryonaut.