This is a nice looking design! I think you're doing great work in making this as dense as possible, and that thick radiator should provide plenty of cooling - I ran my previous setup (Ryzen 1600X + Fury X) with just a single EK PE 240, and your rad is noticeably thicker.
One word of warning: 18mm for the connectors on the bottom is ... well, sketchy. You will need angled adapters for literally every connector, which means you'll lose a lot of I/O as connectors are covered up by others. I measured some of the cables currently connected to my PC, and not a single one is below 18mm for the housing itself, let alone housing + bent cable. The shortest USB 2.0 cable protruded by 20mm at the end of the (short, stiff) strain-relief, with USB-C cables at >30mm and other cables ranging from 25-40mm. The only ones that would pass are my sort of internal (routing from the bottom to the back of the Meshlicious) ADT-link angled DP adapter cables, which stick out 9-10mm (a bit difficult to measure).
I'm also curious as to the intended airflow paths here. You have the PSU intake + a vent behind the motherboard on one side, and radiator fans on the other, with a PSU exhaust on top. With the radiator fans exhausting air, it seems to me that they will likely suck air in through the PSU exhaust vent, as that is the closest vent to the radiator. You have a shroud surrounding the PSU at the top (I'm assuming that is to avoid air being sucked in here?) but if that is effective then there's not many other places for those fans to get air from. The space behind the motherboard is slim and restrictive, plus the air will have to take a long and crooked path to get to the radiator, adding a lot of restriction. Depending on panel fitment you'll have some air creeping in through the cracks, but likely not a lot. So the fans will not only have to fight the radiator's resistance to airflow, but also fight a very restrictive case layout overall. I would be surprised if this didn't change thermals quite noticeably compared to your open-bench mockup. Have you considered boxing in that setup with cardboard or something similar to emulate the final airflow layout?
If you're crazy confident enough to strip your PSU (I would strongly recommend having a perforated metal casing made for it, as PSU switching might swamp your case with RF noise and might make your PCIe riser unusable), you could drastically improve airflow by adding a top fan - it would fit a 140mm fan there, right? Either as an intake with exhaust rad fans, or the opposite, that would provide a lot of fresh air to your components and radiator both.
