u/Acceptable-Body-4280

How will temps be like if I used an external radiator (420mm) with a 58mm thickness rather than a Corsair XR5 280 and an EK CoolStream Classic SE 240?

Specs:
Ryzen 7 7800X3D
Liquid Devil 7900 XTX
Fittings : Undecided
Tubing: 12mm or 14mm and EK ZMT with Quick Disconnects
Pump/Block/Res: EKWB Quantum Velocity 2 DDC 4.2 Pump/Block/Res Unit

I also need advice on which fittings to use? I'm thinking 12mm tubing with Bitspower classic fittings but worried about a leak or the Thermal Grizzly DeltaMate fittings but they only come in 14mm

Can I use the ModUltra with XYLEM 4.3 DDC pump Lobo to cool a ATX PC inside the nzxt H5 Flow? I have a Ryzen 7 7800X3D and 7900 XTX, thanks! I fear I killed the pump inside my EKWB Quantum Velocity 2 DDC 4.2 Pump/Block/Res unit

The CableMod C-Series Pro type 4 black label cables are compatible with the Corsair AX1600i right?

Can't decide if I should buy a leakshield or not? Sorry for the short post

I really am indecisive, I need opinions or some from people on deciding which Motherboard to use. Maxsun B850 Aiga or Nzxt b650e.