Kalunga:
If you use reasonably bulky slow-burning powders, a filler is not needed for either cartridge.

The .470 uses 103gr to 105gr H4831 to match factory ballistics, and the .500 3-inch uses 106gr H4350. There will be a small amount of air-space in the case, but it does not cause problems. These are the recommended factory-load equivalents in Graeme Wright's book, and are in common use in Australia on a daily basis with those exact loads using the original ADI-branded powders and no filler.

If you prefer to use 'Reloader' powders, you will need fillers for sure.

Sorry I cannot advise on Norma, Vitavourhi, Vectan, etc, but you get the idea. Hopefully someone else has experience with European powders, especially the bulky slow-burners.