Just keep in mind what kind of metal your water will interact with since that is all that matters.
Copper and brass = safe
Copper and aluminum = bad
Now you might start to wonder why most manufacturers of radiators use copper and aluminum togetter.
The tubing in the radiator is copper and the chambers is brass and that is the only parts of the radiator that interact with water.
The aluminum / stell housing dont interact with the water so it does not matter. It could have been made out of wood if that matters, since it does not interact with water.
So copper, nickel plated copper, and brass is safe to use in the same loop.
Now I will still strongly suggest you add anti corrosion and anti algae if you want to mix your own fluid with distiled water.
Or just buy premix if unsure how to do that. I would suggest Mayhems as a brand.
Also keep in mind what kind of tubes you use like: Soft tubing, acrylic, PETG, glass, etc etc. Since that can impact what kind of pre-mixed fluid you can use.
Welcome to the wonderfull world of watercooling 😀