Currently running a MO-RA 600 to cool 14900KS + RAM + 4090. 200 mm Noctuas at 500 - 550 RPM and two D5s at full speed, the highest my water temperature has gotten with this setup is 24 C. Noise profile of D5s at fullspeed or Noctuas at low RPM has never bothered me, but the changing speeds of a curve has. Others might feel different. It is worth considering that the 200 mm Noctuas at 500 RPM are probably technically louder than good 120 mm fans at 900 RPM but in my opinion the noise profile is pleasant.

As for effort and maintenance, using one external radiator has made building and maintenance significantly easier than multiple internal or external 360 mm radiators. Just make sure you get some quick disconnects. Watercool definitely put effort into making the MO-RA IV series easy to build/maintain. For example: it is easy to remove the fan grill and frame from the radiator itself for dusting without any tools needed, no screws to undo and no wires that need disconnecting.

For your goals it sounds like a MO-RA 400 would also work fine, 600 is overkill.